Variation in sexual size dimorphism and fit to Rensch's rule in Costa Rican hummingbirds

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Objective : To analyze patterns of SSD in body mass and test Rensch’s rule in 45 species of Costa Rican hummingbirds. Methods : We evaluated SSD in body mass across 45 hummingbird species using Bayesian phylogenetic regression to test for conformity with Rensch’s rule. We hypothesized that physiological constraints would limit SSD variation due to the group’s high metabolic rates, dependence on energy-rich food, and the energetic costs of small size and hovering flight, all of which scale with body mass and elevation. Larger species were expected to tolerate greater SSD variation than smaller, more energetically constrained species. Results : Hummingbirds exhibited mixed allometry and conformed to Rensch’s rule, with a phylogenetic regression slope of male vs. female body mass significantly less than 1 (0.84). Male-biased allometry was observed in 80% of species. On average, SSD variation in body mass was 12% and was significantly associated only with male size. These results suggest that physiological constraints limit the magnitude of SSD variation across the clade, regardless of overall body size. Conclusions : SSD in body mass influences ecological performance, mating displays, resource access, and foraging strategies. The presence of mixed allometry and the positive association between male body mass and SSD support the idea that selective pressures act differently on each sex, potentially promoting sexual niche segregation. Future studies should assess intersexual morphological variation, quantify habitat use and niche partitioning between sexes, and evaluate interspecific and intraspecific competition — particularly in species located at the extremes of the Rensch’s rule continuum. display agility hypothesis hummingbird ecology mating competition hypothesis physiological limits to SSD sexual size dimorphism sexual selection Figures Figure 1 Figure 2 Figure 3 Introduction Differences in body mass between the sexes are widely distributed across a diverse variety of organisms, from vertebrates (Fairbairn 1997) to arthropods (Blanckenhorn et al 2007). This difference in body size between males and females is referred to as sexual size dimorphism (SSD). In birds, SSD varies extensively and is linked to diverse ecological, physiological, and evolutionary processes, including competition for mates, specialization of reproductive roles, predation risk, and resource partitioning (Fairbairn 1997; Blanckenhorn et al 2007). SSD has important selective consequences since it influences trophic niche segregation (i.e., Bravo et al 2016), specialization in reproductive roles, and reproductive success (Kingsolver and Huey 2008; Herczeg et al 2010; Barber et al 2024). A recurring macroevolutionary pattern related to SSD is Rensch’s rule, which predicts that SSD increases with body size when males are larger (positive allometry or hyperallometry), but decreases when females are larger (negative allometry or hypoallometry, Rensch 1950; Blanckenhorn 2005). Both SSD and Rensch’s rule are thought to result from the interaction of sexual selection, ecological niche divergence, and developmental constraints (Andersson 1994; Slatkin 1984; Shuker and Kvarnemo 2021). The underlying causes are multifaceted and, in many cases, the result of the interplay between competition for mates, sexual display agility (Andersson, 1994; Shuker et al 2021), and ecological pressures (e.g., niche segregation, size-dependent survival, e.g., Darwin 1871; Payne 1984; Székely et al 2007; Temeles et al 2010; Maglianesi et al 2022; Barber et al 2024). The interplay between sexual selection and ecological hypotheses is not mutually exclusive and could be operating simultaneously (Andersson 1994). Conditions such as the mating system (e.g., polygyny in lekking species vs. monogamy), and the breeding aggregation of one sex, could intensify intraspecific competition for mates and thus increase the magnitude of SSD through sexual selection. However, sexual selection also acts on non-morphological traits, including vocalizations, plumage, and behavioral displays such as lekking. Additional selective pressures, not directly related to sexual selection, could also act on SSD, such as the increase in brain size in relation to body mass in hummingbirds (see Ocampo et al 2018), which impacts foraging behavior and habitat selection (Gonzalez-Gomez et al 2014). Disentangling the evolution of the allometry of SSD implies understanding many of the key questions in evolutionary biology, such as the evolution of groups of correlated traits, and the influence of phenotype plasticity associated with the expression of SSD. Field studies estimating population parameters affecting the evolution of size and of SSD are needed to distinguish between overlapping hypotheses. Birds present key systems for studying SSD and Rensch’s rule. Numerous comparative and phylogenetic studies across avian orders have shown that both patterns are widespread in birds, with strong links to mating systems, sexual selection intensity, and ecological strategies (Dale et al 2007; Lislevand et al 2007; Székely et al 2007; Cox and Calsbeek 2010; Weeks et al 2020). In many taxa, male-biased SSD is associated with lekking or polygynous systems, while female-biased SSD appears in raptors and other groups subject to fecundity or ecological selection. Although sexual selection is often cited as the primary driver of SSD in birds, its interaction with ecological pressures, especially under varying energetic constraints, remains incompletely understood (Blanckenhorn 2005; Zhou et al 2024). Natural and sexual selection, as well as physical and physiological constraints, set sex-specific upper and lower limits on body mass, and thus define the extent of variation in SSD (Zhou et al (2024). Hummingbirds (Trochilidae) offer an exceptional model for studying SSD and Rensch’s rule since they exhibit a broad range of SSD, including mixed allometries, with species in which females are the larger sex, as well as species in which males are larger. Some hummingbirds show sex segregation in habitat and resource use (Howell and Gardali 2003; Leimberger et al 2022). Males and females have distinctive reproductive roles and polygynous reproductive systems, where leks are prevalent. Some hummingbirds may have reached the upper energetic limits of miniaturization of any group of flying vertebrates, adapting their physiology to conserve heat in cold nights in some of the higher elevation habitats colonized by small vertebrates (Shankar et al 2022). Their high metabolic rates force them to secure almost constant access to high-energy food sources, in addition to placing severe constraints on their ability to deal with environmental variation, although this has not been an obstacle for the colonization of high-altitude habitats (Altshuler and Dudley 2002). The quality of food resources, as well as morphological limitations in accessing floral resources, impacted the evolution of hummingbird morphology and physiology due to considerable energy constraints associated with miniaturization and their high dependency on nectar consumption (see Kessler et al 2020). However, the degree to which hummingbirds conform to Rensch’s rule, and the underlying mechanisms constraining SSD, remain incompletely understood (Colwell 2000; Ocampo et al 2018). Organismic responses to environmental change are strongly influenced by body size, which varies along a continuous gradient, intra and interspecifically (Peters 1986). Smaller species, with their higher surface-area-to-volume ratios, typically exhibit faster physiological responses and greater plasticity to short-term environmental fluctuations. However, their limited energy reserves make them more susceptible to extreme or prolonged stresses, such as resource shortages or temperature extremes. In contrast, larger species generally have greater energy reserves and lower relative metabolic rates, enabling them to buffer or tolerate environmental changes over longer periods, though they may not respond as rapidly to acute fluctuations (Blanckenhorn 2005; Cox and Calsbeek 2010). These contrasting strategies, mediated by the scale and intensity of environmental changes, can shape both intra- and interspecific variation in body size and influence patterns of sexual size dimorphism (SSD), as individuals of different sizes and sexes exploit distinct ecological niches and microhabitats. Empirical studies in birds reflect these dynamics since climate warming has been associated with increased variation in body size traits, demonstrating the interplay of selective pressures and plastic responses (Zimova et al 2023). For instance, Weeks et al (2020) found that reductions in body size among migratory birds may enhance thermal adaptability, a trend often offset by increased wing length to maintain flight efficiency. Nonetheless, the evidence remains mixed, as body size is shaped by a complex interplay of genetic, environmental, and selective factors (Nord et al 2024). Overall, these findings highlight the central role of body size in determining species resilience and guiding evolutionary responses to changing climatic conditions. This study aims to quantify SSD and evaluate the fit to Rensch’s rule across 45 species of hummingbirds. By integrating comparative analyses with current phylogenetic methods and leveraging the substantial avian literature on the drivers of SSD, we seek to clarify how ecological, physiological, and evolutionary processes interact to shape SSD in this clade. We include species spanning a wide body size range, from the largest hummingbird in Costa Rica, the Violet Sabrewing ( Campylopterus hemileucurus ), to the smallest species, the Scintillant Hummingbird ( Selasphorus scintilla ). We hypothesize that the physiological capacity for buffering environmental changes, which increases with body mass, can explain differences in the extent of SSD variation among species. Specifically, large-bodied species, with greater energy reserves and enhanced ability to tolerate periods of environmental stress, may allow for greater ecological and morphological divergence between males and females, resulting in a wider range of SSD. In contrast, small-bodied species, being more energetically constrained and less able to buffer resource shortages, should present a smaller range of morphological variation between males and females. Greater variation in SSD in larger species could also reinforce sexual niche segregation. Our results will emphasize the importance of examining male- and female-biased allometries and help establish future directions for understanding the ecological and evolutionary significance of SSD in hummingbirds. Materials and Methods Sources of morphological data: We compiled body mass data for 45 species of Costa Rican hummingbirds from three sources: (a) our own field database of 19 hummingbird species representing 731 mist net captures registered between 2012 and 2016 at multiple sites in Costa Rica, (b) museum specimens (n = 154) representing 35 species from the ornithological collection of the Museum of Zoology at the University of Costa Rica; and (c) species accounts on the Birds of the World online platform (https://birdsoftheworld.org/bow/home?) hosted by the Cornell Lab of Ornithology. These sources provided body mass values (in grams), a morphological trait commonly reported in the literature and museum databases, and one that is ecologically meaningful due to its correlation with resource acquisition and energetic demands (Dalsgaard et al 2009). This composite dataset, referred to as the “large dataset” (Table 1), served as the basis for our analyses of sexual size dimorphism (SSD). We classified species into eight of the nine major hummingbird clades following McGuire et al (2014): Bees, Coquettes, Hermits, Brilliants, Emeralds, Mangoes, Mountain Gems, and Topazes. Lovich-Gibbons sexual dimorphism index: We quantified sexual size dimorphism (SSD) in body mass using the Lovich–Gibbons index (Lovich and Gibbons, 1992), calculated as the ratio of the average body mass of the larger sex to that of the smaller sex, minus one: SSD index = (larger sex / smaller sex) − 1 By convention, the index is positive when females are the larger sex and assigned a negative value when males are larger. As a ratio, the index can also be interpreted as a percentage. For example, in Selasphorus flammula , the index value is 0.096 (Table 1), indicating that females are 9.6% larger than males. The Lovich–Gibbons index values across species followed a normal distribution (Shapiro–Wilk test: W = 0.96, P = 0.28). Statistical Analyses: We designated male body mass as the predictor and female body mass as the response variable, following standard convention in studies of SSD (e.g., Colwell, 2000). To test the hypothesis that SSD increases with body size, consistent with Rensch’s rule, we used Bayesian linear regression models implemented in the brms package in R (Bürkner, 2017). Specifically, we fit Gaussian Bayesian models to examine the relationship between the absolute value of SSD (as calculated by the Lovich–Gibbons index) and the body mass of both males and females. To account for phylogenetic non-independence and uncertainty, we used a set of 100 phylogenetic trees from the posterior distribution published by McGuire et al (2014). A phylogenetic covariance matrix derived from these trees was incorporated as a random effect in the models. Posterior distributions of model parameters from each tree were combined into a single model fit, allowing us to account for evolutionary relationships and shared ancestry among species. All analyses were conducted in R version 3.6.0 (R Core Team, 2019). Results We observed substantial variation in body mass across species, ranging from the largest male, the Violet Sabrewing ( Campylopterus hemileucurus , 12.42 g, n = 11), and the largest female, the White-tipped Sicklebill ( Eutoxeres aquila , 10.11 g), to the smallest species, the Scintillant Hummingbird ( Selasphorus scintilla ), with males averaging 2.05 g and females 2.30 g (Table 1). Fit to Rensch´s Rule: We found a significant relationship between the log₁₀-transformed body mass of males and females across species (Fig. 1; Table 2; intercept = 0.09, slope = 0.84). The slope was significantly less than 1, consistent with Rensch’s rule, and indicates mixed allometry (i.e., larger, male-biased species occurred at the upper end of the distribution, while smaller, female-biased species clustered at the lower end of the scatterplot). The magnitude of SSD increased significantly with male body mass (Table 2; intercept = 0.01, slope = 0.15), but not with female body mass (intercept = 0.05, slope = 0.10; Fig. 2), further supporting a male-driven allometric pattern. Patterns of SSD varied among phylogenetic clades. Based on the Lovich–Gibbons index, Bees and Coquettes generally exhibited female-biased SSD (positive values), whereas larger-bodied clades, such as Brilliants, Topazes, and Mountain Gems, tended to exhibit male-biased SSD (negative values; Fig. 3). Notably, some species within the Mangoes, Emeralds, and Hermits clades showed female-biased SSD, although the overall trend within these groups remained male-biased. Of the 45 species examined, 36 (80%) exhibited male-biased SSD. Test of the hypothesis of physiological limits to SSD associated with body mass: Although hummingbirds overall conformed to Rensch’s rule with mixed allometry, nearly half of the species (48%, n = 22) exhibited modest variation in SSD for body mass (<10%, Table 1, Fig. 3). Eighteen species showed SSD values exceeding 10%, including C. hemileucurus , Lampornis castaneoventris , Colibri delphinae , and Microchera cupreiceps , which all displayed SSD greater than 30%. Except for C. hemileucurus , these were mid-sized species (4–8 g). The largest species, C. hemileucurus , exhibited pronounced male-biased SSD, in which males were, on average, 36% heavier than females. Our observations indicate that male C. hemileucurus dominate competitive interactions at artificial feeders, displacing conspecific females and individuals from six mid-sized species. Conversely, six mid-sized species ( Threnetes ruckeri , Glaucis aeneus , Microchera albocoronata , Chlorestes candida , Heliothryx barroti , and Saucerottia hoffmanni ) showed less than 5% SSD variation. Only five species, including small Bees, Coquettes, and the Stripe-throated Hermit ( Phaethornis striigularis , mean body mass 2.6 g), exhibited reversed sexual dimorphism (RSD), with SSD ranging from 10% to 17%. Thus, while our prediction that larger species show greater SSD variation was supported for large and some mid-sized species, the expectation that smaller species display lower SSD variation was not supported by the data. The relationship between body mass and the absolute value of the Lovich–Gibbons ratio (Fig. 2) was significant for males but not for females, indicating stronger selection pressures on increasing dimorphism with male body size. Across the 45 species, the average absolute Lovich–Gibbons ratio was 0.12 ± 0.08, reflecting a moderate, overall male-biased SSD of approximately 12%. Discussion Our findings on SSD align with Rensch’s rule: larger hummingbird species exhibit male-biased SSD, whereas smaller species tend to show female-biased or less pronounced male-biased SSD. This scaling pattern, common across animal taxa (Abouheif and Fairbairn 1997; Székely et al 2007), suggests that selection acts differently across the body size spectrum of males and females, consistent with the evolutionary allometries predicted by Rensch’s rule (Caron and Pie 2025). The proximate mechanisms we discuss, such as aerodynamic constraints favoring more agile males in small species, sexual selection for increased fecundity in females due to reproductive costs (Caron and Pie 2025), and competitive advantages favoring larger males in larger species, likely drive these macroevolutionary trends. Thus, our data not only highlight species- and sex-specific selective pressures shaping SSD but also provide support for its allometric evolution. This interpretation is reinforced by Colwell’s (2000) comparative analysis of 154 hummingbird species, which also found mixed allometry and reported the same slope value (0.84) observed in our study. Furthermore, based on the criterion proposed by Abouheif and Fairbairn (1997), that a taxon can be classified as male-biased if 80% or more of its species show larger males, our sample meets this threshold: 80% of the 45 hummingbird species analyzed exhibited male-biased SSD in body mass. Larger males may gain advantages in competing for food and access to mates through physical combat. However, in species that exhibit reversed sexual size dimorphism (RSD), where females are larger, selection may favor smaller males for enhanced maneuverability and larger females for greater reproductive capacity (Caron and Pie 2025). In the case of the aerial agility hypothesis (Raihani et al 2006), such differences in morphology may promote intersexual niche divergence, as males and females experience distinct selective pressures (Bravo et al 2024). In smaller species, for example, males often perform complex, acrobatic courtship displays, where aerodynamic traits such as wing area and wing loading can increase reproductive success (e.g., the elaborate aerial displays of Selasphorus flammula and S. scintilla ; Clark et al 2011). In these small species, the energetic cost of reproduction (e.g., egg production) is proportionally greater for females, potentially favoring a larger female body size (Wheeler and Greenwood 1983). Other hypotheses may also contribute to the observed SSD patterns. The intersexual niche divergence hypothesis posits that size differences between sexes reduce competition for food, while the small-male hypothesis suggests that smaller males forage more efficiently (Krüger 2005). These mechanisms are likely to interact to produce the variation in SSD observed among large and small hummingbird species (Bravo et al 2024). Sexual selection also plays a role, as evidenced by sexual dimorphism in plumage coloration and the presence of exaggerated male traits such as elongated tail, crown, and throat feathers, which may also relate to body mass and flight agility (Caron and Pie 2025). Although direct experimental evidence is lacking to test these hypotheses, our findings provide a valuable foundation for future research. For instance, in S. flammula (SSD = 9.6%), we documented intersexual habitat segregation, in which males were more frequently observed in páramo vegetation above the tree line, whereas females predominantly occupied forest edges, canopy gaps, and the interior of oak forests. Comparable patterns of habitat segregation have also been reported for S. sasin and S. rufus in California, where males and females forage in distinct habitats (Howell and Gardali 2003). Causes of variation in SSD: The average absolute variation in sexual size dimorphism (SSD) in body mass across species was 12%, a value we consider moderate (Fairbairn 2007). Rather than scaling strictly with body mass, our findings suggest that physiological constraints may limit SSD across hummingbirds as a group, regardless of size. Hummingbirds exhibit extremely high metabolic rates, a strong dependence on near-constant access to energy-rich food sources, and substantial energetic costs due to small body size and hovering flight. These physiological demands may constrain overall body mass variation, as well as SSD, despite the presence of sex-specific selective pressures. Contrary to our expectations, we did not observe a consistent trend of increasing SSD variation from smaller to larger species. We hypothesized that larger hummingbirds would exhibit greater SSD, while smaller species, constrained by energetic limitations, would show reduced variation. This prediction also assumed that higher SSD would promote greater intersexual niche differentiation. However, our results showed relatively modest SSD variation across species (see also Székely et al 2007). While we might expect variation in SSD to correspond with functional differences, such as competitive ability or resource partitioning (Maglianesi et al 2022), hummingbirds exhibit high behavioral plasticity that may buffer the ecological consequences of morphological divergence (Rodríguez et al 2023). Differences in size, though relevant to determining competitive hierarchies and access to resources, can be offset by opportunistic foraging strategies and behaviors such as nectar robbing (Ornelas 1994; Boehm 2018). This behavioral flexibility likely facilitates access to floral resources across the full spectrum of body sizes, reducing the selective pressure for more pronounced morphological divergence between sexes. Notably, the relationship between body mass and the absolute value of SSD increased with species size only in males. This pattern suggests that selection may act more strongly on male body size, potentially contributing to intersexual niche segregation. However, the underlying mechanisms remain unclear and warrant further investigation through field studies that quantify both intersexual and intraspecific morphological variation. Finally, it is important to recognize a limitation of most SSD analyses: the use of average values for morphological traits, often derived from museum specimens and small sample sizes, tends to obscure the true range of variation within and between sexes. This issue has been previously noted (Smith 1999). As shown in our study, relying solely on male-to-female ratios of trait means masks meaningful patterns of variation, particularly when one sex shows high variability in a given trait. Future studies should incorporate measures of dispersion to better understand the functional and evolutionary significance of SSD. Other morphological traits influencing SSD: While body mass is the most frequently analyzed trait in studies of SSD (Fairbairn 1997; Colwell 2000), it is not the only morphological characteristic that affects competitive performance, foraging strategies, or resource access. One reason for its prominence is that body mass is routinely recorded in both field studies and museum specimens. However, a broader exploration of additional traits is necessary to fully understand the ecological and evolutionary implications of SSD. For example, the size of the hallux (rear toe) can influence foraging efficiency. In some mountain gem species, such as Panterpe insignis , relatively large legs and a well-developed hallux allow individuals to perch while feeding, thereby reducing the energetic costs associated with hovering flight (R. Colwell pers. comm.). Similarly, bill morphology plays a key role in determining access to floral resources. Long-billed hummingbirds can exploit a wider range of corolla lengths than short-billed species, enabling both legitimate and illegitimate (nectar-robbing) visits (Rojas-Rodríguez et al 2023). Opportunistic and generalized foraging strategies are widespread in pollination networks, further highlighting the importance of flexible bill traits (Simmons et al 2019). In addition to bill length, bill shape and specialized structures, such as serrations along the edges, can influence foraging for both nectar and arthropods (Feinsinger and Colwell 1978; Rico-Guevara et al 2019). These serrations, which enable piercing of corollas during nectar robbing, also facilitate insect capture and may function as secondary sexual traits that enhance male–male competition (Ornelas 1994; Rico-Guevara and Araya-Salas 2015). Conclusion The mixed allometry in SSD observed in this study indicates that males and females experience distinct selective pressures on body mass. In large species, sexual selection may favor increased male size, while in smaller species, selection may instead prioritize greater male agility and buffer reproductive costs in females. We hypothesized that physiological constraints associated with body mass would explain the variation in SSD, expecting greater divergence in larger species. Contrary to this expectation, average variation in SSD was modest (12%) and significantly related to body mass only in males. This limited range of variation likely reflects the overarching influence of physiological limitations that constrain SSD in hummingbirds as a group, regardless of overall size. Importantly, the behavioral plasticity of hummingbirds appears to mitigate morphological constraints on resource access. Traits such as bill length, curvature, and the presence of bill striae may enhance foraging flexibility, facilitating nectar robbing, insect predation, and male–male competition in certain species. Our study underscores the need to analyze sexual size dimorphism (SSD) within an integrative framework that combines evolutionary allometries, such as Rensch’s rule, with ecological, behavioral, and physiological mechanisms. To advance this understanding, future research should prioritize field-based studies that measure a broader range of morphological traits, document habitat and resource use, and quantify behavioral and ecological segregation between sexes. Focusing only on average trait ratios between males and females overlooks intraspecific and intersexual variation, which can obscure the selective pressures acting on each sex. Since our findings reveal mixed allometry, suggesting that different traits may evolve under distinct selective regimes in males and females, it is essential to incorporate variation around trait means. Field studies should also examine intersexual niche segregation, courtship behaviors, and both intra- and interspecific competition, particularly in species that lie at the extremes of the Rensch’s rule continuum. Declarations ACKNOWLEDGMENTS Keilor Rojas Jiménez facilitated the participation of FT and JK and triggered the writing of this manuscript. Robert Colwell read an early version of this manuscript and made comments that significantly improved the final version. Ignacio Gutiérrez allowed access to the ornithology database of the Museum of Zoology at the University of Costa Rica. Jim McGuire facilitated the phylogenetic data. We thank Génesis Coto for her initial comments on data collection. Funding : this research was supported by The School for Field Studies and the University of Costa Rica. Conflicts of interest : the authors express no conflicts of interest. Ethics approval : the authors expressed they followed the Committee on Publication Ethics (COPE) regulations. Consent to participate : all the authors agreed to contribute intellectually to this research. Consent for publication : all the authors approved the last version of the manuscript. Availability of data and material : The data used in this publication is included in the Supplementary Materials. Authors' contributions : GA conceived the idea, collected the field data, and wrote the manuscript. FT and JK Contributed data. All authors analyzed the data and edited the manuscript. 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Anim Behav 71(4):833–838 Rensch B Die Abhängigkeit der relativen Sexualdifferenz von der Körpergrösse. Bonner Zoologische Beiträge 1:58-69Rico-Guevara A, Araya-Salas M (1950) (2015) Bills as daggers? A test for sexually dimorphic weapons in a lekking hummingbird. Behav Ecol 26(1):21–29 Rico-Guevara A, Rubega MA, Hurme KJ et al (2019) Shifting paradigms in the mechanics of nectar extraction and hummingbird bill morphology. IOB 1(1):oby006 Rojas-Rodríguez P, Bianchi-Barrantes S, Avalos G (2023) Efecto de la longitud del pico sobre la especialización de la visitación floral de colibríes de zonas medias y altas de Costa Rica. Zeledonia 27(1):1–17 Shankar A, Cisneros INH, Thompson S et al (2022) A heterothermic spectrum in hummingbirds. J Exp Bio 225:jeb243208 Shuker DM, Kvarnemo C (2021) The definition of sexual selection. Behav Ecol 32(5):781–794 Simmons BI, Vizentin-Bugoni J, Maruyama PK et al (2019) Abundance drives broad patterns of generalisation in plant–hummingbird pollination networks. Oikos 128(9):1287–1295 Slatkin M (1984) Ecological causes of sexual dimorphism. Evol 38(3):622–630 Smith RJ (1999) Statistics of sexual size dimorphism. J Hum Evol 36(4):423–458 Székely T, Lislevand T, Figuerola J (2007) Sexual size dimorphism in birds. In: Fairbairn DJ, Blanckenhorn WU, Székely T (eds) Sex, size and gender roles: evolutionary studies of sexual size dimorphism, Oxford, UK, pp 27–37 Temeles EJ, Miller JS, Rifkin JL (2010) Evolution of sexual dimorphism in bill size and shape of hermit hummingbirds (Phaethornithinae): a role for ecological causation. Philos T R Soc B 365(1543):1053–1063 Weeks BC, Willard DE, Zimova M, Ellis AA, Witynski ML, Hennen M, Winger BM (2020) Shared morphological consequences of global warming in North American migratory birds. Ecol Lett 23(2):316–325 Wheeler P, Greenwood PJ (1983) The evolution of reversed sexual dimorphism in birds of prey. Oikos 40(1):145–149 Zhou Y, Pan Y, Wang M, Wang X, Zheng X, Zhou Z (2024) Fossil evidence sheds light on sexual selection during the early evolution of birds. Proc Natl Acad Sci USA 121(3):e2309825120 Zimova M, Weeks BC, Willard DE, Giery ST, Jirinec V, Burner RC, Winger BM (2023) Body size predicts the rate of contemporary morphological change in birds. Proc Natl Acad Sci USA 120(20):e2206971120 Tables TABLE 1 Body mass (g) and Lovich-Gibbons sexual dimorphism index of the 45 hummingbird species considered in this study according to phylogenetic clade and sex. Phylogenetic clades follow the classification of McGuire et al (2014). Common name Scientific name Phylogenetic clade Body mass of male Body mass of female Lovich-Gibbons ratio Magenta-throated Woodstar Philodice bryantae Bees 3.3 3.5 0.061 Ruby-throated Hummingbird Archilochus colubris 2.7 3 0.111 Scintillant Hummingbird Selasphorus scintilla 2.05 2.3 0.122 Volcano Hummingbird Selasphorus flammula 2.5 2.74 0.096 Green-crowned Brilliant Heliodoxa jacula Billiants 9.06 8.54 -0.061 Black-crested Coquette Lophornis helenae Coquettes 2.15 2.52 0.172 Green Thorntail Discosura conversii 3.1 2.9 -0.069 Black-bellied Hummingbird Eupherusa nigriventris Emeralds 3.425 3.25 -0.054 Blue-chested Hummingbird Polyerata amabilis 4 3.8 -0.053 Blue-throated Goldentail Chlorestes eliciae 3.8 3.3 -0.152 Blue-vented Hummingbird Saucerottia hoffmanni 4.4 4.3 -0.023 Bronze-tailed Plumeleteer Chalybura urochrysia 7.1 6.1 -0.164 Cinnamon Hummingbird Amazilia rutila 4.9 4.2 -0.167 Coppery-headed Emerald Microchera cupreiceps 4.7 3.64 -0.291 Crowned Woodnymph Thalurania colombica 4.5 4 -0.125 Mangrove Hummingbird Amazilia boucardi 4.95 4.2 -0.179 Rufous-tailed Hummingbird Amazilia tzacatl 4.82 4.54 -0.062 Scaly-breasted hummingbird Phaeochroa cuvierii 9.38 8.6 -0.091 Snowcap Microchera albocoronata 2.48 2.56 0.032 Snowy-bellied Hummingbird Saucerottia edward 5 4.3 -0.163 Stripe-tailed Hummingbird Eupherusa eximia 4.68 4.06 -0.153 Violet Sabrewing Campylopterus hemileucurus 12.42 9.18 -0.353 Violet-headed Hummingbird Klais guimeti 2.9 2.7 -0.074 White-bellied Emerald Chlorestes candida 3.7 3.8 0.026 White-tailed Emerald Microchera chonura 3.3 3.1 -0.065 Band-tailed Barbthroat Threnetes ruckeri Hermits 6.09 5.82 -0.046 Bronzy Hermit Glaucis aeneus 5.08 4.9 -0.037 Green Hermit Phaetornis guy 5.9 5.6 -0.054 Long-tailed Hermit Phaethornis superciliosus 6.04 5.65 -0.069 Stripe-throated Hermit Phaethornis striigularis 2.43 2.69 0.107 White-tipped Sicklebill Eutoxeres aquila 10.80 10.11 -0.068 Brown Violet-ear Colibri delphinae Mangoes 8 6.1 -0.311 Green-breasted Mango Anthracothorax prevostii 6.90 6.15 -0.122 Green-fronted Lancebill Doryfera ludovicae 5.9 5.5 -0.073 Lesser Violetear Colibri cyanotus 5.3 4.8 -0.104 Purple-crowned Fairy Heliothryx barroti 5.5 5.63 0.024 Canivet's Emerald Cynanthus canivetii Mountain Gems 2.5 2.3 -0.087 Fiery-throated Hummingbird Panterpe insignis 5.9 4.9 -0.204 Gray-tailed Mountain-gem Lampornis castaneoventris 5.86 4.35 -0.347 Long-billed Starthroat Heliomaster longisrostris 6.04 5.65 -0.069 Plain-capped Starthroat Heliomaster constantii 8.2 7.15 -0.147 Purple-throated Mountain-gem Lampornis calolaemus 5.9 5.2 -0.135 Talamanca Hummingbird Eugenes spectabilis 10.54 9.31 -0.132 White-bellied Mountain-gem Lampornis hemileucus 6.2 5 -0.240 White-necked Jacobin Florisuga mellivora Topazes 7.4 6 -0.233 TABLE 2 Summary of the results from the Bayesian Phylogenetic models used to asses Rensch’s rule and variation in SSD expressed as the Lovich-Gibbons Index. Model Formula Parameters Estimate l-95% CI u-95% CI Rhat log10(Female weight) ~ log10(Male weight) log10(female weight) ~ log10(male weight) + (1 | gr(Species, cov = phy.tree)) Intercept 0.09 0.04 0.14 1.00 Slope 0.84 0.78 0.90 1.00 SSD (Lovich-Gibbons Ratio) ~ log10(Male weight) Lovich-Gibbons Ratio ~ log10(male weight) + (1 | gr(Species, cov = phy.tree)) Intercept 0.01 -0.10 0.11 1.00 Slope 0.15 0.02 0.29 1.00 SSD (Lovich-Gibbons Ratio) ~ log10(Female weight) Lovich-Gibbons Ratio ~ log10(female weight) + (1 | gr(Species, cov = phy.tree)) Intercept 0.05 -0.07 0.17 1.00 Slope 0.10 -0.06 0.26 1.00 Additional Declarations No competing interests reported. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-7190180","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":494818476,"identity":"1f5b1a37-2fbe-45a5-af0a-bcccea40cb2b","order_by":0,"name":"Gerardo Avalos","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA/ElEQVRIiWNgGAWjYBAC/gYQyQZmMx5gYLAhrEXiAEILA5CdRliLAQOqlsNEaGHvffi5osyGgX9G8oMDH/6cT+yffYDxww8Gu3ycWniOG0ueOZfGIHEjzeDgzLbbiTPOJTBL9jAkWzbg0GJ4I41BsrEN6J4zBwwO8zbcTtzAw8AgDXSkAU5b7j9j/gnSIn/m+IfDPH/OgbQw/8ar5QYbG9gWg+M9Bod52A6AtLDhtUXiTBqbZcO5NB7D4z0FQL8kG884w9hm2WOQjFMLf/sx5psNZTZycofZNz748MdOtr+H+fCNHxV2OLXAAA8Sm7EBFl+jYBSMglEwCsgEAG1KVmRtPQ40AAAAAElFTkSuQmCC","orcid":"","institution":"Universidad de Costa Rica","correspondingAuthor":true,"prefix":"","firstName":"Gerardo","middleName":"","lastName":"Avalos","suffix":""},{"id":494818477,"identity":"94ec2336-a8a9-47f7-9256-433ca6d67cc9","order_by":1,"name":"Felipe Triana","email":"","orcid":"","institution":"Universidad de Costa Rica","correspondingAuthor":false,"prefix":"","firstName":"Felipe","middleName":"","lastName":"Triana","suffix":""},{"id":494818481,"identity":"7009aa44-f40f-401d-9aa0-4bc04fdef00a","order_by":2,"name":"Jeremy Klank","email":"","orcid":"","institution":"Universidad de Costa Rica","correspondingAuthor":false,"prefix":"","firstName":"Jeremy","middleName":"","lastName":"Klank","suffix":""},{"id":494818484,"identity":"cf261a51-2097-45ce-8554-dd9c1694c515","order_by":3,"name":"Marcelo Araya","email":"","orcid":"","institution":"Universidad de Costa Rica","correspondingAuthor":false,"prefix":"","firstName":"Marcelo","middleName":"","lastName":"Araya","suffix":""}],"badges":[],"createdAt":"2025-07-22 20:08:12","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-7190180/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-7190180/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1007/s10682-026-10389-0","type":"published","date":"2026-02-19T15:58:26+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":88342775,"identity":"34ae69a5-a41d-4439-b801-fbd5cce0cab4","added_by":"auto","created_at":"2025-08-05 13:05:58","extension":"jpeg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":46492,"visible":true,"origin":"","legend":"\u003cp\u003eRensch’s rule in hummingbirds across Costa Rica. We built the regression from 45 species from Costa Rica and subjected the data to a phylogenetic correction.\u003c/p\u003e","description":"","filename":"floatimage1.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7190180/v1/220bacfa7b418e875ddda319.jpeg"},{"id":88342781,"identity":"5cabe0f0-28f4-4a55-bab5-74c3e39bbad4","added_by":"auto","created_at":"2025-08-05 13:05:58","extension":"jpeg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":297611,"visible":true,"origin":"","legend":"\u003cp\u003eRegression between the absolute sexual size dimorphism (Lovich-Gibbons Ratio) and the Log10 body mass of each sex. We perform the analyzes from 45 Costa Rican hummingbird species that underwent a phylogenetic correction.\u003c/p\u003e","description":"","filename":"floatimage2.jpeg","url":"https://assets-eu.researchsquare.com/files/rs-7190180/v1/e1ff99bb4dce8dce90d0553a.jpeg"},{"id":88342777,"identity":"4c1ec47c-bb9c-4f17-8945-8bbf012b0c69","added_by":"auto","created_at":"2025-08-05 13:05:58","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":90250,"visible":true,"origin":"","legend":"\u003cp\u003eVariation in the Lovich-Gibbons ratio for SSD in body mass among eight hummingbird clades following McGuire et al (2014). Below zero, there is a male-biased allometry, and above zero there is female-biased allometry.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-7190180/v1/43d09cc94d6b0ece363a2a9b.png"},{"id":103251543,"identity":"89884c27-96c6-4d04-8d8f-c334bb202401","added_by":"auto","created_at":"2026-02-23 16:10:38","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1158631,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7190180/v1/9b89ae01-3062-42f1-b701-65d10932d9e1.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"Variation in sexual size dimorphism and fit to Rensch's rule in Costa Rican hummingbirds","fulltext":[{"header":"Introduction","content":"\u003cp\u003eDifferences in body mass between the sexes are widely distributed across a diverse variety of organisms, from vertebrates (Fairbairn 1997) to arthropods (Blanckenhorn et al 2007). This difference in body size between males and females is referred to as \u003cem\u003esexual size dimorphism\u003c/em\u003e (SSD). In birds, SSD varies extensively and is linked to diverse ecological, physiological, and evolutionary processes, including competition for mates, specialization of reproductive roles, predation risk, and resource partitioning (Fairbairn 1997; Blanckenhorn et al 2007). SSD has important selective consequences since it influences trophic niche segregation (i.e., Bravo et al 2016), specialization in reproductive roles, and reproductive success (Kingsolver and Huey 2008; Herczeg et al 2010; Barber et al 2024). A recurring macroevolutionary pattern related to SSD is Rensch’s rule, which predicts that SSD increases with body size when males are larger (positive allometry or hyperallometry), but decreases when females are larger (negative allometry or hypoallometry, Rensch 1950; Blanckenhorn 2005). Both SSD and Rensch’s rule are thought to result from the interaction of sexual selection, ecological niche divergence, and developmental constraints (Andersson 1994; Slatkin 1984; Shuker and Kvarnemo 2021). The underlying causes are multifaceted and, in many cases, the result of the interplay between competition for mates, sexual display agility (Andersson, 1994; Shuker et al 2021), and ecological pressures (e.g., niche segregation, size-dependent survival, e.g., Darwin 1871; Payne 1984; Székely et al 2007; Temeles et al 2010; Maglianesi et al 2022; Barber et al 2024).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe interplay between sexual selection and ecological hypotheses is not mutually exclusive and could be operating simultaneously (Andersson 1994). Conditions such as the mating system (e.g., polygyny in lekking species vs. monogamy), and the breeding aggregation of one sex, could intensify intraspecific competition for mates and thus increase the magnitude of SSD through sexual selection. However, sexual selection also acts on non-morphological traits, including vocalizations, plumage, and behavioral displays such as lekking. Additional selective pressures, not directly related to sexual selection, could also act on SSD, such as the increase in brain size in relation to body mass in hummingbirds (see Ocampo et al 2018), which impacts foraging behavior and habitat selection (Gonzalez-Gomez et al 2014). Disentangling the evolution of the allometry of SSD implies understanding many of the key questions in evolutionary biology, such as the evolution of groups of correlated traits, and the influence of phenotype plasticity associated with the expression of SSD. Field studies estimating population parameters affecting the evolution of size and of SSD are needed to distinguish between overlapping hypotheses.\u003c/p\u003e\n\u003cp\u003eBirds present key systems for studying SSD and Rensch’s rule. Numerous comparative and phylogenetic studies across avian orders have shown that both patterns are widespread in birds, with strong links to mating systems, sexual selection intensity, and ecological strategies (Dale et al 2007; Lislevand et al 2007; Székely et al 2007; Cox and Calsbeek 2010; Weeks et al 2020). In many taxa, male-biased SSD is associated with lekking or polygynous systems, while female-biased SSD appears in raptors and other groups subject to fecundity or ecological selection. Although sexual selection is often cited as the primary driver of SSD in birds, its interaction with ecological pressures, especially under varying energetic constraints, remains incompletely understood (Blanckenhorn 2005; Zhou et al 2024). Natural and sexual selection, as well as physical and physiological constraints, set sex-specific upper and lower limits on body mass, and thus define the extent of variation in SSD (Zhou et al (2024).\u003c/p\u003e\n\u003cp\u003eHummingbirds (Trochilidae) offer an exceptional model for studying SSD and Rensch’s rule since they exhibit a broad range of SSD, including mixed allometries, with species in which females are the larger sex, as well as species in which males are larger. Some hummingbirds show sex segregation in habitat and resource use (Howell and Gardali 2003; Leimberger et al 2022). Males and females have distinctive reproductive roles and polygynous reproductive systems, where leks are prevalent. Some hummingbirds may have reached the upper energetic limits of miniaturization of any group of flying vertebrates, adapting their physiology to conserve heat in cold nights in some of the higher elevation habitats colonized by small vertebrates (Shankar et al 2022). Their high metabolic rates force them to secure almost constant access to high-energy food sources, in addition to placing severe constraints on their ability to deal with environmental variation, although this has not been an obstacle for the colonization of high-altitude habitats (Altshuler and Dudley 2002). The quality of food resources, as well as morphological limitations in accessing floral resources, impacted the evolution of hummingbird morphology and physiology due to considerable energy constraints associated with miniaturization and their high dependency on nectar consumption (see Kessler et al 2020). However, the degree to which hummingbirds conform to Rensch’s rule, and the underlying mechanisms constraining SSD, remain incompletely understood (Colwell 2000; Ocampo et al 2018).\u003c/p\u003e\n\u003cp\u003eOrganismic responses to environmental change are strongly influenced by body size, which varies along a continuous gradient, intra and interspecifically (Peters 1986). Smaller species, with their higher surface-area-to-volume ratios, typically exhibit faster physiological responses and greater plasticity to short-term environmental fluctuations. However, their limited energy reserves make them more susceptible to extreme or prolonged stresses, such as resource shortages or temperature extremes. In contrast, larger species generally have greater energy reserves and lower relative metabolic rates, enabling them to buffer or tolerate environmental changes over longer periods, though they may not respond as rapidly to acute fluctuations (Blanckenhorn 2005; Cox and Calsbeek 2010). These contrasting strategies, mediated by the scale and intensity of environmental changes, can shape both intra- and interspecific variation in body size and influence patterns of sexual size dimorphism (SSD), as individuals of different sizes and sexes exploit distinct ecological niches and microhabitats. Empirical studies in birds reflect these dynamics since climate warming has been associated with increased variation in body size traits, demonstrating the interplay of selective pressures and plastic responses (Zimova et al 2023). For instance, Weeks et al (2020) found that reductions in body size among migratory birds may enhance thermal adaptability, a trend often offset by increased wing length to maintain flight efficiency. Nonetheless, the evidence remains mixed, as body size is shaped by a complex interplay of genetic, environmental, and selective factors (Nord et al 2024). Overall, these findings highlight the central role of body size in determining species resilience and guiding evolutionary responses to changing climatic conditions.\u003c/p\u003e\n\u003cp\u003eThis study aims to quantify SSD and evaluate the fit to Rensch’s rule across 45 species of hummingbirds. By integrating comparative analyses with current phylogenetic methods and leveraging the substantial avian literature on the drivers of SSD, we seek to clarify how ecological, physiological, and evolutionary processes interact to shape SSD in this clade. We include species spanning a wide body size range, from the largest hummingbird in Costa Rica, the Violet Sabrewing (\u003cem\u003eCampylopterus hemileucurus\u003c/em\u003e), to the smallest species, the Scintillant Hummingbird (\u003cem\u003eSelasphorus scintilla\u003c/em\u003e). We hypothesize that the physiological capacity for buffering environmental changes, which increases with body mass, can explain differences in the extent of SSD variation among species. Specifically, large-bodied species, with greater energy reserves and enhanced ability to tolerate periods of environmental stress, may allow for greater ecological and morphological divergence between males and females, resulting in a wider range of SSD. In contrast, small-bodied species, being more energetically constrained and less able to buffer resource shortages, should present a smaller range of morphological variation between males and females. Greater variation in SSD in larger species could also reinforce sexual niche segregation. Our results will emphasize the importance of examining male- and female-biased allometries and help establish future directions for understanding the ecological and evolutionary significance of SSD in hummingbirds.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cp\u003e\u003cstrong\u003eSources of morphological data:\u0026nbsp;\u003c/strong\u003eWe compiled body mass data for 45 species of Costa Rican hummingbirds from three sources: (a) our own field database of 19 hummingbird species representing 731 mist net captures registered between 2012 and 2016 at multiple sites in Costa Rica, (b) museum specimens (n = 154) representing 35 species from the ornithological collection of the Museum of Zoology at the University of Costa Rica; and (c) species accounts on the Birds of the World online platform (https://birdsoftheworld.org/bow/home?) hosted by the Cornell Lab of Ornithology. These sources provided body mass values (in grams), a morphological trait commonly reported in the literature and museum databases, and one that is ecologically meaningful due to its correlation with resource acquisition and energetic demands (Dalsgaard et al 2009). This composite dataset, referred to as the \u0026ldquo;large dataset\u0026rdquo; (Table 1), served as the basis for our analyses of sexual size dimorphism (SSD). We classified species into eight of the nine major hummingbird clades following McGuire et al (2014): Bees, Coquettes, Hermits, Brilliants, Emeralds, Mangoes, Mountain Gems, and Topazes.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eLovich-Gibbons sexual dimorphism index:\u0026nbsp;\u003c/strong\u003eWe quantified sexual size dimorphism (SSD) in body mass using the Lovich\u0026ndash;Gibbons index (Lovich and Gibbons, 1992), calculated as the ratio of the average body mass of the larger sex to that of the smaller sex, minus one:\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSSD\u0026nbsp;index = (larger\u0026nbsp;sex / smaller\u0026nbsp;sex) \u0026minus; 1\u003c/p\u003e\n\u003cp\u003eBy convention, the index is positive when females are the larger sex and assigned a negative value when males are larger. As a ratio, the index can also be interpreted as a percentage. For example, in \u003cem\u003eSelasphorus flammula\u003c/em\u003e, the index value is 0.096 (Table 1), indicating that females are 9.6% larger than males. The Lovich\u0026ndash;Gibbons index values across species followed a normal distribution (Shapiro\u0026ndash;Wilk test: W = 0.96, P = 0.28).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eStatistical Analyses:\u0026nbsp;\u003c/strong\u003eWe designated male body mass as the predictor and female body mass as the response variable, following standard convention in studies of SSD (e.g., Colwell, 2000). To test the hypothesis that SSD increases with body size, consistent with Rensch\u0026rsquo;s rule, we used Bayesian linear regression models implemented in the brms package in R (B\u0026uuml;rkner, 2017). Specifically, we fit Gaussian Bayesian models to examine the relationship between the absolute value of SSD (as calculated by the Lovich\u0026ndash;Gibbons index) and the body mass of both males and females. To account for phylogenetic non-independence and uncertainty, we used a set of 100 phylogenetic trees from the posterior distribution published by McGuire et al (2014). A phylogenetic covariance matrix derived from these trees was incorporated as a random effect in the models. Posterior distributions of model parameters from each tree were combined into a single model fit, allowing us to account for evolutionary relationships and shared ancestry among species. All analyses were conducted in R version 3.6.0 (R Core Team, 2019).\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003eWe observed substantial variation in body mass across species, ranging from the largest male, the Violet Sabrewing (\u003cem\u003eCampylopterus hemileucurus\u003c/em\u003e, 12.42 g, n = 11), and the largest female, the White-tipped Sicklebill (\u003cem\u003eEutoxeres aquila\u003c/em\u003e, 10.11 g), to the smallest species, the Scintillant Hummingbird (\u003cem\u003eSelasphorus scintilla\u003c/em\u003e), with males averaging 2.05 g and females 2.30 g (Table 1).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFit to Rensch´s Rule:\u0026nbsp;\u003c/strong\u003eWe found a significant relationship between the log₁₀-transformed body mass of males and females across species (Fig. 1; Table 2; intercept = 0.09, slope = 0.84). The slope was significantly less than 1, consistent with Rensch’s rule, and indicates mixed allometry (i.e., larger, male-biased species occurred at the upper end of the distribution, while smaller, female-biased species clustered at the lower end of the scatterplot). The magnitude of SSD increased significantly with male body mass (Table 2; intercept = 0.01, slope = 0.15), but not with female body mass (intercept = 0.05, slope = 0.10; Fig. 2), further supporting a male-driven allometric pattern. Patterns of SSD varied among phylogenetic clades. Based on the Lovich–Gibbons index, Bees and Coquettes generally exhibited female-biased SSD (positive values), whereas larger-bodied clades, such as Brilliants, Topazes, and Mountain Gems, tended to exhibit male-biased SSD (negative values; Fig. 3). Notably, some species within the Mangoes, Emeralds, and Hermits clades showed female-biased SSD, although the overall trend within these groups remained male-biased. Of the 45 species examined, 36 (80%) exhibited male-biased SSD.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTest of the hypothesis of physiological limits to SSD associated with body mass:\u0026nbsp;\u003c/strong\u003eAlthough hummingbirds overall conformed to Rensch’s rule with mixed allometry, nearly half of the species (48%, n = 22) exhibited modest variation in SSD for body mass (\u0026lt;10%, Table 1, Fig. 3). Eighteen species showed SSD values exceeding 10%, including \u003cem\u003eC. hemileucurus\u003c/em\u003e, \u003cem\u003eLampornis castaneoventris\u003c/em\u003e, \u003cem\u003eColibri delphinae\u003c/em\u003e, and \u003cem\u003eMicrochera cupreiceps\u003c/em\u003e, which all displayed SSD greater than 30%. Except for \u003cem\u003eC. hemileucurus\u003c/em\u003e, these were mid-sized species (4–8 g). The largest species, \u003cem\u003eC. hemileucurus\u003c/em\u003e, exhibited pronounced male-biased SSD, in which males were, on average, 36% heavier than females. Our observations indicate that male \u003cem\u003eC. hemileucurus\u003c/em\u003e dominate competitive interactions at artificial feeders, displacing conspecific females and individuals from six mid-sized species.\u003c/p\u003e\n\u003cp\u003eConversely, six mid-sized species (\u003cem\u003eThrenetes ruckeri\u003c/em\u003e, \u003cem\u003eGlaucis aeneus\u003c/em\u003e, \u003cem\u003eMicrochera albocoronata\u003c/em\u003e, \u003cem\u003eChlorestes candida\u003c/em\u003e, \u003cem\u003eHeliothryx barroti\u003c/em\u003e, and \u003cem\u003eSaucerottia hoffmanni\u003c/em\u003e) showed less than 5% SSD variation. Only five species, including small Bees, Coquettes, and the Stripe-throated Hermit (\u003cem\u003ePhaethornis striigularis\u003c/em\u003e, mean body mass 2.6 g), exhibited reversed sexual dimorphism (RSD), with SSD ranging from 10% to 17%. Thus, while our prediction that larger species show greater SSD variation was supported for large and some mid-sized species, the expectation that smaller species display lower SSD variation was not supported by the data.\u003c/p\u003e\n\u003cp\u003eThe relationship between body mass and the absolute value of the Lovich–Gibbons ratio (Fig. 2) was significant for males but not for females, indicating stronger selection pressures on increasing dimorphism with male body size. Across the 45 species, the average absolute Lovich–Gibbons ratio was 0.12 ± 0.08, reflecting a moderate, overall male-biased SSD of approximately 12%.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eOur findings on SSD align with Rensch’s rule: larger hummingbird species exhibit male-biased SSD, whereas smaller species tend to show female-biased or less pronounced male-biased SSD. This scaling pattern, common across animal taxa (Abouheif and Fairbairn 1997; Székely et al 2007), suggests that selection acts differently across the body size spectrum of males and females, consistent with the evolutionary allometries predicted by Rensch’s rule (Caron and Pie 2025). The proximate mechanisms we discuss, such as aerodynamic constraints favoring more agile males in small species, sexual selection for increased fecundity in females due to reproductive costs (Caron and Pie 2025), and competitive advantages favoring larger males in larger species, likely drive these macroevolutionary trends. Thus, our data not only highlight species- and sex-specific selective pressures shaping SSD but also provide support for its allometric evolution. This interpretation is reinforced by Colwell’s (2000) comparative analysis of 154 hummingbird species, which also found mixed allometry and reported the same slope value (0.84) observed in our study. Furthermore, based on the criterion proposed by Abouheif and Fairbairn (1997), that a taxon can be classified as male-biased if 80% or more of its species show larger males, our sample meets this threshold: 80% of the 45 hummingbird species analyzed exhibited male-biased SSD in body mass.\u003c/p\u003e\n\u003cp\u003eLarger males may gain advantages in competing for food and access to mates through physical combat. However, in species that exhibit reversed sexual size dimorphism (RSD), where females are larger, selection may favor smaller males for enhanced maneuverability and larger females for greater reproductive capacity (Caron and Pie 2025). In the case of the aerial agility hypothesis (Raihani et al 2006), such differences in morphology may promote intersexual niche divergence, as males and females experience distinct selective pressures (Bravo et al 2024). In smaller species, for example, males often perform complex, acrobatic courtship displays, where aerodynamic traits such as wing area and wing loading can increase reproductive success (e.g., the elaborate aerial displays of \u003cem\u003eSelasphorus flammula\u003c/em\u003e and \u003cem\u003eS. scintilla\u003c/em\u003e; Clark et al 2011). In these small species, the energetic cost of reproduction (e.g., egg production) is proportionally greater for females, potentially favoring a larger female body size (Wheeler and Greenwood 1983).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eOther hypotheses may also contribute to the observed SSD patterns. The intersexual niche divergence hypothesis posits that size differences between sexes reduce competition for food, while the small-male hypothesis suggests that smaller males forage more efficiently (Krüger 2005). These mechanisms are likely to interact to produce the variation in SSD observed among large and small hummingbird species (Bravo et al 2024). Sexual selection also plays a role, as evidenced by sexual dimorphism in plumage coloration and the presence of exaggerated male traits such as elongated tail, crown, and throat feathers, which may also relate to body mass and flight agility (Caron and Pie 2025).\u003c/p\u003e\n\u003cp\u003eAlthough direct experimental evidence is lacking to test these hypotheses, our findings provide a valuable foundation for future research. For instance, in \u003cem\u003eS. flammula\u003c/em\u003e (SSD = 9.6%), we documented intersexual habitat segregation, in which males were more frequently observed in páramo vegetation above the tree line, whereas females predominantly occupied forest edges, canopy gaps, and the interior of oak forests. Comparable patterns of habitat segregation have also been reported for \u003cem\u003eS. sasin\u003c/em\u003e and \u003cem\u003eS. rufus\u003c/em\u003e in California, where males and females forage in distinct habitats (Howell and Gardali 2003).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCauses of variation in SSD:\u0026nbsp;\u003c/strong\u003eThe average absolute variation in sexual size dimorphism (SSD) in body mass across species was 12%, a value we consider moderate (Fairbairn 2007). Rather than scaling strictly with body mass, our findings suggest that physiological constraints may limit SSD across hummingbirds as a group, regardless of size. Hummingbirds exhibit extremely high metabolic rates, a strong dependence on near-constant access to energy-rich food sources, and substantial energetic costs due to small body size and hovering flight. These physiological demands may constrain overall body mass variation, as well as SSD, despite the presence of sex-specific selective pressures.\u003c/p\u003e\n\u003cp\u003eContrary to our expectations, we did not observe a consistent trend of increasing SSD variation from smaller to larger species. We hypothesized that larger hummingbirds would exhibit greater SSD, while smaller species, constrained by energetic limitations, would show reduced variation. This prediction also assumed that higher SSD would promote greater intersexual niche differentiation. However, our results showed relatively modest SSD variation across species (see also Székely et al 2007).\u003c/p\u003e\n\u003cp\u003eWhile we might expect variation in SSD to correspond with functional differences, such as competitive ability or resource partitioning (Maglianesi et al 2022), hummingbirds exhibit high behavioral plasticity that may buffer the ecological consequences of morphological divergence (Rodríguez et al 2023). Differences in size, though relevant to determining competitive hierarchies and access to resources, can be offset by opportunistic foraging strategies and behaviors such as nectar robbing (Ornelas 1994; Boehm 2018). This behavioral flexibility likely facilitates access to floral resources across the full spectrum of body sizes, reducing the selective pressure for more pronounced morphological divergence between sexes.\u003c/p\u003e\n\u003cp\u003eNotably, the relationship between body mass and the absolute value of SSD increased with species size only in males. This pattern suggests that selection may act more strongly on male body size, potentially contributing to intersexual niche segregation. However, the underlying mechanisms remain unclear and warrant further investigation through field studies that quantify both intersexual and intraspecific morphological variation.\u003c/p\u003e\n\u003cp\u003eFinally, it is important to recognize a limitation of most SSD analyses: the use of average values for morphological traits, often derived from museum specimens and small sample sizes, tends to obscure the true range of variation within and between sexes. This issue has been previously noted (Smith 1999). As shown in our study, relying solely on male-to-female ratios of trait means masks meaningful patterns of variation, particularly when one sex shows high variability in a given trait. Future studies should incorporate measures of dispersion to better understand the functional and evolutionary significance of SSD.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eOther morphological traits influencing SSD:\u0026nbsp;\u003c/strong\u003eWhile body mass is the most frequently analyzed trait in studies of SSD (Fairbairn 1997; Colwell 2000), it is not the only morphological characteristic that affects competitive performance, foraging strategies, or resource access. One reason for its prominence is that body mass is routinely recorded in both field studies and museum specimens. However, a broader exploration of additional traits is necessary to fully understand the ecological and evolutionary implications of SSD. For example, the size of the hallux (rear toe) can influence foraging efficiency. In some mountain gem species, such as \u003cem\u003ePanterpe insignis\u003c/em\u003e, relatively large legs and a well-developed hallux allow individuals to perch while feeding, thereby reducing the energetic costs associated with hovering flight (R. Colwell pers. comm.). Similarly, bill morphology plays a key role in determining access to floral resources. Long-billed hummingbirds can exploit a wider range of corolla lengths than short-billed species, enabling both legitimate and illegitimate (nectar-robbing) visits (Rojas-Rodríguez et al 2023). Opportunistic and generalized foraging strategies are widespread in pollination networks, further highlighting the importance of flexible bill traits (Simmons et al 2019).\u003c/p\u003e\n\u003cp\u003eIn addition to bill length, bill shape and specialized structures, such as serrations along the edges, can influence foraging for both nectar and arthropods (Feinsinger and Colwell 1978; Rico-Guevara et al 2019). These serrations, which enable piercing of corollas during nectar robbing, also facilitate insect capture and may function as secondary sexual traits that enhance male–male competition (Ornelas 1994; Rico-Guevara and Araya-Salas 2015).\u003c/p\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThe mixed allometry in SSD observed in this study indicates that males and females experience distinct selective pressures on body mass. In large species, sexual selection may favor increased male size, while in smaller species, selection may instead prioritize greater male agility and buffer reproductive costs in females. We hypothesized that physiological constraints associated with body mass would explain the variation in SSD, expecting greater divergence in larger species. Contrary to this expectation, average variation in SSD was modest (12%) and significantly related to body mass only in males. This limited range of variation likely reflects the overarching influence of physiological limitations that constrain SSD in hummingbirds as a group, regardless of overall size. Importantly, the behavioral plasticity of hummingbirds appears to mitigate morphological constraints on resource access. Traits such as bill length, curvature, and the presence of bill striae may enhance foraging flexibility, facilitating nectar robbing, insect predation, and male–male competition in certain species.\u003c/p\u003e\n\u003cp\u003eOur study underscores the need to analyze sexual size dimorphism (SSD) within an integrative framework that combines evolutionary allometries, such as Rensch’s rule, with ecological, behavioral, and physiological mechanisms. To advance this understanding, future research should prioritize field-based studies that measure a broader range of morphological traits, document habitat and resource use, and quantify behavioral and ecological segregation between sexes. Focusing only on average trait ratios between males and females overlooks intraspecific and intersexual variation, which can obscure the selective pressures acting on each sex. Since our findings reveal mixed allometry, suggesting that different traits may evolve under distinct selective regimes in males and females, it is essential to incorporate variation around trait means. Field studies should also examine intersexual niche segregation, courtship behaviors, and both intra- and interspecific competition, particularly in species that lie at the extremes of the Rensch’s rule continuum.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003eACKNOWLEDGMENTS\u003c/p\u003e\n\u003cp\u003eKeilor Rojas Jiménez facilitated the participation of FT and JK and triggered the writing of this manuscript. Robert Colwell read an early version of this manuscript and made comments that significantly improved the final version. Ignacio Gutiérrez allowed access to the ornithology database of the Museum of Zoology at the University of Costa Rica. Jim McGuire facilitated the phylogenetic data. We thank Génesis Coto for her initial comments on data collection.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding\u003c/strong\u003e: this research was supported by The School for Field Studies and the University of Costa Rica.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflicts of interest\u003c/strong\u003e: the authors express no conflicts of interest.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval\u003c/strong\u003e: the authors expressed they followed the Committee on Publication Ethics (COPE) regulations.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent to participate\u003c/strong\u003e: all the authors agreed to contribute intellectually to this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication\u003c/strong\u003e: all the authors approved the last version of the manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and material\u003c/strong\u003e: The data used in this publication is included in the Supplementary Materials.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors' contributions\u003c/strong\u003e: GA conceived the idea, collected the field data, and wrote the manuscript. FT and JK Contributed data. All authors analyzed the data and edited the manuscript.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eAbouheif E, Fairbairn DJ (1997) A comparative analysis of allometry for sexual size dimorphism: assessing Rensch's rule. Am Nat 149(3):540\u0026ndash;562\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAndersson M (1994) Sexual selection. Princeton University Press, Princeton\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eAltshuler DL, Dudley R (2002) The ecological and evolutionary interface of hummingbird flight physiology. J Exp Biol 205(16):2325\u0026ndash;2336\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eBarber RA, Yang J, Yang C, Barker O, Janicke T, Tobias JA (2024) Climate and ecology predict latitudinal trends in sexual selection inferred from avian mating systems. 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Behav Ecol 26(1):21\u0026ndash;29\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRico-Guevara A, Rubega MA, Hurme KJ et al (2019) Shifting paradigms in the mechanics of nectar extraction and hummingbird bill morphology. IOB 1(1):oby006\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eRojas-Rodr\u0026iacute;guez P, Bianchi-Barrantes S, Avalos G (2023) Efecto de la longitud del pico sobre la especializaci\u0026oacute;n de la visitaci\u0026oacute;n floral de colibr\u0026iacute;es de zonas medias y altas de Costa Rica. Zeledonia 27(1):1\u0026ndash;17\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShankar A, Cisneros INH, Thompson S et al (2022) A heterothermic spectrum in hummingbirds. J Exp Bio 225:jeb243208\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eShuker DM, Kvarnemo C (2021) The definition of sexual selection. Behav Ecol 32(5):781\u0026ndash;794\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSimmons BI, Vizentin-Bugoni J, Maruyama PK et al (2019) Abundance drives broad patterns of generalisation in plant\u0026ndash;hummingbird pollination networks. Oikos 128(9):1287\u0026ndash;1295\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSlatkin M (1984) Ecological causes of sexual dimorphism. Evol 38(3):622\u0026ndash;630\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSmith RJ (1999) Statistics of sexual size dimorphism. J Hum Evol 36(4):423\u0026ndash;458\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSz\u0026eacute;kely T, Lislevand T, Figuerola J (2007) Sexual size dimorphism in birds. In: Fairbairn DJ, Blanckenhorn WU, Sz\u0026eacute;kely T (eds) Sex, size and gender roles: evolutionary studies of sexual size dimorphism, Oxford, UK, pp 27\u0026ndash;37\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTemeles EJ, Miller JS, Rifkin JL (2010) Evolution of sexual dimorphism in bill size and shape of hermit hummingbirds (Phaethornithinae): a role for ecological causation. Philos T R Soc B 365(1543):1053\u0026ndash;1063\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWeeks BC, Willard DE, Zimova M, Ellis AA, Witynski ML, Hennen M, Winger BM (2020) Shared morphological consequences of global warming in North American migratory birds. Ecol Lett 23(2):316\u0026ndash;325\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eWheeler P, Greenwood PJ (1983) The evolution of reversed sexual dimorphism in birds of prey. Oikos 40(1):145\u0026ndash;149\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZhou Y, Pan Y, Wang M, Wang X, Zheng X, Zhou Z (2024) Fossil evidence sheds light on sexual selection during the early evolution of birds. Proc Natl Acad Sci USA 121(3):e2309825120\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eZimova M, Weeks BC, Willard DE, Giery ST, Jirinec V, Burner RC, Winger BM (2023) Body size predicts the rate of contemporary morphological change in birds. Proc Natl Acad Sci USA 120(20):e2206971120\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTABLE 1\u003c/p\u003e\n\u003cp\u003eBody mass (g) and Lovich-Gibbons sexual dimorphism index of the 45 hummingbird species considered in this study according to phylogenetic clade and sex. Phylogenetic clades follow the classification of McGuire et al (2014).\u003c/p\u003e\n\u003cp\u003e\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"714\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eCommon name\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003eScientific name\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003ePhylogenetic clade\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003eBody mass of male\u003c/p\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003eBody mass of female\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 71px;\"\u003e\n \u003cp\u003eLovich-Gibbons ratio\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eMagenta-throated Woodstar\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003ePhilodice bryantae\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003eBees\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.061\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eRuby-throated Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eArchilochus colubris\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.111\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eScintillant Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eSelasphorus scintilla\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.122\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eVolcano Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eSelasphorus flammula\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.74\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.096\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eGreen-crowned Brilliant\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eHeliodoxa jacula\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003eBilliants\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e9.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e8.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.061\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBlack-crested Coquette\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eLophornis helenae\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003eCoquettes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.52\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.172\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eGreen Thorntail\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eDiscosura conversii\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.069\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBlack-bellied Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eEupherusa nigriventris\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003eEmeralds\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.425\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.25\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.054\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBlue-chested Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003ePolyerata amabilis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.053\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBlue-throated Goldentail\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eChlorestes eliciae\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.152\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBlue-vented Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eSaucerottia hoffmanni\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.023\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBronze-tailed Plumeleteer\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eChalybura urochrysia\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e7.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.164\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eCinnamon Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eAmazilia rutila\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.167\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eCoppery-headed Emerald\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eMicrochera cupreiceps\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.64\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.291\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eCrowned Woodnymph\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eThalurania colombica\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.125\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eMangrove Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eAmazilia boucardi\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.95\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.179\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eRufous-tailed Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eAmazilia tzacatl\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.062\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eScaly-breasted hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003ePhaeochroa cuvierii\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e9.38\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e8.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.091\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eSnowcap\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eMicrochera albocoronata\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.48\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.56\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.032\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eSnowy-bellied Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eSaucerottia edward\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.163\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eStripe-tailed Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eEupherusa eximia\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.68\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.153\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eViolet Sabrewing\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eCampylopterus hemileucurus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e12.42\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e9.18\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.353\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eViolet-headed Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eKlais guimeti\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.074\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eWhite-bellied Emerald\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eChlorestes candida\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.7\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.026\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eWhite-tailed Emerald\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eMicrochera chonura\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e3.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.065\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBand-tailed Barbthroat\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eThrenetes ruckeri\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003eHermits\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.82\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.046\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBronzy Hermit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eGlaucis aeneus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.08\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.037\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eGreen Hermit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003ePhaetornis guy\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.054\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eLong-tailed Hermit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003ePhaethornis superciliosus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.069\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eStripe-throated Hermit\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003ePhaethornis striigularis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.43\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.69\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.107\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eWhite-tipped Sicklebill\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eEutoxeres aquila\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e10.80\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e10.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.068\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eBrown Violet-ear\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eColibri delphinae\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003eMangoes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6.1\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.311\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eGreen-breasted Mango\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eAnthracothorax prevostii\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.122\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eGreen-fronted Lancebill\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eDoryfera ludovicae\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.073\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eLesser Violetear\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eColibri cyanotus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.8\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.104\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003ePurple-crowned Fairy\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eHeliothryx barroti\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.63\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e0.024\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eCanivet\u0026apos;s Emerald\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eCynanthus canivetii\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003eMountain Gems\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e2.3\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.087\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eFiery-throated Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003ePanterpe insignis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.204\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eGray-tailed Mountain-gem\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eLampornis castaneoventris\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.86\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e4.35\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.347\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eLong-billed Starthroat\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eHeliomaster longisrostris\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.65\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.069\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003ePlain-capped Starthroat\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eHeliomaster constantii\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e8.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e7.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.147\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003ePurple-throated Mountain-gem\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eLampornis calolaemus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.9\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.135\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eTalamanca Hummingbird\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eEugenes spectabilis\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e10.54\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e9.31\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.132\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eWhite-bellied Mountain-gem\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eLampornis hemileucus\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003e\u0026nbsp;\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6.2\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e5\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.240\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"bottom\" style=\"width: 215px;\"\u003e\n \u003cp\u003eWhite-necked Jacobin\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 193px;\"\u003e\n \u003cp\u003e\u003cem\u003eFlorisuga mellivora\u003c/em\u003e\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 107px;\"\u003e\n \u003cp\u003eTopazes\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e7.4\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"bottom\" style=\"width: 64px;\"\u003e\n \u003cp\u003e6\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd style=\"width: 71px;\"\u003e\n \u003cp\u003e-0.233\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n\u003cp\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003eTABLE 2\u003c/p\u003e\n\u003cp\u003eSummary of the results from the Bayesian Phylogenetic models used to asses Rensch\u0026rsquo;s rule and variation in SSD expressed as the Lovich-Gibbons Index.\u0026nbsp;\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\" width=\"624\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003eModel\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eFormula\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eParameters\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003eEstimate\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003el-95% CI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003eu-95% CI\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003eRhat\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003elog10(Female weight) ~ log10(Male weight)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003elog10(female weight) ~ log10(male weight) + (1 | gr(Species, cov = phy.tree))\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eIntercept\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.09\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.04\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.14\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eSlope\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.84\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.78\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.90\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003eSSD (Lovich-Gibbons Ratio) ~ log10(Male weight)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eLovich-Gibbons Ratio ~ log10(male weight) + (1 | gr(Species, cov = phy.tree))\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eIntercept\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.01\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e-0.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.11\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eSlope\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.15\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.02\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.29\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 101px;\"\u003e\n \u003cp\u003eSSD (Lovich-Gibbons Ratio) ~ log10(Female weight)\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd rowspan=\"2\" valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eLovich-Gibbons Ratio ~ log10(female weight) + (1 | gr(Species, cov = phy.tree))\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eIntercept\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.05\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e-0.07\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.17\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\" style=\"width: 160px;\"\u003e\n \u003cp\u003eSlope\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.10\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e-0.06\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e0.26\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\" style=\"width: 51px;\"\u003e\n \u003cp\u003e1.00\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e\n"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"evolutionary-ecology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"evec","sideBox":"Learn more about [Evolutionary Ecology](https://www.springer.com/journal/10682)","snPcode":"10682","submissionUrl":"https://submission.nature.com/new-submission/10682/3","title":"Evolutionary Ecology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"display agility hypothesis, hummingbird ecology, mating competition hypothesis, physiological limits to SSD, sexual size dimorphism, sexual selection","lastPublishedDoi":"10.21203/rs.3.rs-7190180/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7190180/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eIntroduction\u003c/strong\u003e: Rensch’s rule predicts that sexual size dimorphism (SSD) increases with body mass in species where males are larger but decreases when females are larger.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eObjective\u003c/strong\u003e: To analyze patterns of SSD in body mass and test Rensch’s rule in 45 species of Costa Rican hummingbirds.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods\u003c/strong\u003e: We evaluated SSD in body mass across 45 hummingbird species using Bayesian phylogenetic regression to test for conformity with Rensch’s rule. We hypothesized that physiological constraints would limit SSD variation due to the group’s high metabolic rates, dependence on energy-rich food, and the energetic costs of small size and hovering flight, all of which scale with body mass and elevation. Larger species were expected to tolerate greater SSD variation than smaller, more energetically constrained species.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eResults\u003c/strong\u003e: Hummingbirds exhibited mixed allometry and conformed to Rensch’s rule, with a phylogenetic regression slope of male vs. female body mass significantly less than 1 (0.84). Male-biased allometry was observed in 80% of species. On average, SSD variation in body mass was 12% and was significantly associated only with male size. These results suggest that physiological constraints limit the magnitude of SSD variation across the clade, regardless of overall body size.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConclusions\u003c/strong\u003e: SSD in body mass influences ecological performance, mating displays, resource access, and foraging strategies. The presence of mixed allometry and the positive association between male body mass and SSD support the idea that selective pressures act differently on each sex, potentially promoting sexual niche segregation. Future studies should assess intersexual morphological variation, quantify habitat use and niche partitioning between sexes, and evaluate interspecific and intraspecific competition — particularly in species located at the extremes of the Rensch’s rule continuum.\u003c/p\u003e","manuscriptTitle":"Variation in sexual size dimorphism and fit to Rensch's rule in Costa Rican hummingbirds","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-05 13:05:54","doi":"10.21203/rs.3.rs-7190180/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2025-10-06T16:40:18+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-09-30T16:52:44+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"17269112053567709541215316884991736941","date":"2025-09-15T20:43:55+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2025-08-08T11:54:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"319479371658438955953663738001950137648","date":"2025-08-03T04:46:19+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-07-31T17:37:05+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-07-23T08:42:54+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2025-07-23T08:41:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"Evolutionary Ecology","date":"2025-07-22T19:58:52+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"evolutionary-ecology","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"evec","sideBox":"Learn more about [Evolutionary Ecology](https://www.springer.com/journal/10682)","snPcode":"10682","submissionUrl":"https://submission.nature.com/new-submission/10682/3","title":"Evolutionary Ecology","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"3a3447d6-7e83-4a81-bedc-a87c0321f1e7","owner":[],"postedDate":"August 5th, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-23T16:06:43+00:00","versionOfRecord":{"articleIdentity":"rs-7190180","link":"https://doi.org/10.1007/s10682-026-10389-0","journal":{"identity":"evolutionary-ecology","isVorOnly":false,"title":"Evolutionary Ecology"},"publishedOn":"2026-02-19 15:58:26","publishedOnDateReadable":"February 19th, 2026"},"versionCreatedAt":"2025-08-05 13:05:54","video":"","vorDoi":"10.1007/s10682-026-10389-0","vorDoiUrl":"https://doi.org/10.1007/s10682-026-10389-0","workflowStages":[]},"version":"v1","identity":"rs-7190180","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7190180","identity":"rs-7190180","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}