Nest architectural traits and reproductive success of blackbird Turdus merula in a Mediterranean forest: implications for population dynamics in northeastern Algeria

Nest architectural traits and reproductive success of blackbird Turdus merula in a Mediterranean forest: implications for population dynamics in northeastern Algeria | Authorea try { document.documentElement.classList.add('js'); } catch (e) { } var _gaq = _gaq || []; _gaq.push(['_setAccount', 'G-8VDV14Y67G']); _gaq.push(['_trackPageview']); (function() { var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true; ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js'; var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s); })(); Skip to main content Preprints Collections Wiley Open Research IET Open Research Ecological Society of Japan All Collections About About Authorea FAQs Contact Us Quick Search anywhere Search for preprint articles, keywords, etc. Search Search ADVANCED SEARCH SCROLL This is a preprint and has not been peer reviewed. Data may be preliminary. 1 April 2026 V1 Latest version Share on Nest architectural traits and reproductive success of blackbird Turdus merula in a Mediterranean forest: implications for population dynamics in northeastern Algeria Authors : Abdelhak Boucif , Mouslim Bara 0000-0003-3818-424X [email protected] , and A. Mohammad Al Kadiri Authors Info & Affiliations https://doi.org/10.22541/au.177500553.31100074/v1 171 views 77 downloads Contents Abstract Supplementary Material Information & Authors Metrics & Citations View Options References Figures Tables Media Share Abstract The blackbird Turdus merula is a widespread passerine whose breeding ecology in North African Mediterranean forests remains poorly documented. We investigated nest architecture, breeding performance, and spatial patterns of this species in Machroha forest (Souk Ahras province, northeastern Algeria), over four breeding seasons (2020–2023). A total of 76 nests were monitored across two forest sections (Razgoun and Mghassel). Nest height, diameter, and depth showed moderate interannual and site-specific variation, while clutch size remained stable across years. Chick production varied among years, with 2020 showing reduced fledging success. Spatial autocorrelation revealed largely random patterns both for nest placement and reproductive output, suggesting homogeneous habitat quality and territory spacing, although nest depth exhibited significant local clustering. Nest height positively influenced chick survival, whereas diameter and depth did not, highlighting the role of vertical placement in mitigating predation and optimizing microclimate conditions. PCA mixed to clustering indicated that nest size and height represented independent axes of architectural variation, reflecting the species’ behavioral plasticity. Overall, Machroha forest provides suitable breeding habitat for blackbirds, with nest architecture exhibiting adaptive flexibility and chick survival responding to subtle nest structural traits. This study fills a critical knowledge gap for North African populations, situating them within Mediterranean and European ecological contexts, and provides essential baseline data for conservation and long-term monitoring in northeast Algerian forest. Introduction Algeria hosts a rich avifauna, with forest ecosystems playing a key role in sustaining diverse bird communities. Mediterranean oak-dominated forests, in particular, provide essential resources such as food, shelter, and nesting sites for breeding passerines (Ceia and Ramos 2016). These ecosystems represent important habitats where ecological processes shape species distribution, community structure, and breeding success (Newton 1998, Begon et al. 2006). Most studies conducted in forest environments have primarily focused on describing bird assemblages or assessing the effects of habitat fragmentation and biogeographical patterns (Raherilalao 2001, Selmi et al. 2002, Boucif et al. 2022). While these approaches have improved our understanding of bird diversity, fewer studies have examined the ecological mechanisms underlying reproductive strategies and breeding performance in relation to nests variability. From an ecological perspective, species coexistence within bird communities is strongly influenced by niche dynamics. Niche overlap among species of the same guild may lead to competition, ecological shifts, or exclusion processes (Schoener 1974, Connell 1980, Begon et al. 2006). In this framework, reproduction represents a central component of the realized niche, as it depends on a multidimensional combination of environmental conditions and resource availability. Breeding is also a key aspect of phenotypic plasticity, allowing species to adjust their strategies in response to environmental variability (Via et al. 1995). In Mediterranean ecosystems, where climatic conditions are highly variable, reproductive output is often influenced by temporal fluctuations, particularly during the nestling period when resource availability becomes critical (Both et al. 2010, Ibáñez-Álamo et al. 2015, Peñuelas et al. 2017). Habitat architectural plays a major role in shaping reproductive strategies, especially through its influence on nest-site selection, predation risk, and microclimatic conditions. Vegetation complexity can affect both nest placement and breeding success, while also contributing to spatial organization patterns within bird populations (Møller et al. 2014, Mainwaring et al. 2014). In this context, the blackbird Turdus merula represents a suitable model species due to its wide distribution and marked ecological flexibility (Zeraoula et al. 2015). It exhibits significant plasticity in habitat use, nest-site selection, and nesting behavior, allowing it to adapt to a wide range of environmental conditions (Grégoire, 2003). This adaptability makes it particularly relevant for investigating how ecological factors influence reproductive performance and nesting strategies. Despite the extensive research conducted on European populations, studies on the breeding ecology of the blackbird in North African forest ecosystems remain limited. This gap restricts our understanding of how Mediterranean forests gradients and local structures influence reproductive dynamics in Algerian populations. This study examines the breeding ecology of the blackbird Turdus merula in Machroha Forest (Souk Ahras province, northeast Algeria). Specifically, it aims to (I) assess breeding performance, (II) analyze nest architectural traits and their variability, and (III) investigate spatial patterns of reproductive parameters. By providing multi-year data from a semi-natural Mediterranean forest, this study contributes to improving knowledge on Northeastern African blackbird population and offers a baseline for understanding how nest variability may affect forest bird populations. Material and methods Study area The Machroha forest (36°21′26″ N and 7°50′8″ E, see Figure 1) represents an important component of Algeria’s forest heritage. Several studies have been conducted on vegetation and reflecting the ecological significance of the area. The total forested area is estimated at 16.750 ha, corresponding to about 5% of the Souk Ahras province (Boucif et al. 2022, Saouli et al. 2022). Vegetation in Machroha is diverse, including cork oak forests Quercus suber , Zeen oak forests Quercus canariensis , cork oak woodlands, Cistus -dominated maquis, and sub-Mediterranean garrigues. Other common species include olive trees Olea europaea , mastic Pistacia lentiscus , Atlas pistachio Pistacia atlantica , myrtle Myrtus communis , and eucalyptus Eucalyptus spp. The region is characterized by rugged mountainous terrain, with elevations ranging from 218 m (Mghassel and Djamela) to 1.315 m (Razgoun and Mahbouba) (Figure 1). The climate of Machroha is Mediterranean, with mild and moderate conditions. Summers and autumns are hot and dry, while winters are wet and rainy. Minimum temperatures are recorded in January, reaching as low as 1.1°C, and maximum temperatures occur in July and August, reaching up to 38°C in Djamela and Mghassel. Annual precipitation ranges around 1.000 mm, increasing between November and April, with values up to 1.013 mm in Razgoun and Mahbouba. Relative humidity varies according to exposure and wind type, with average monthly values ranging between 59% and 73% (Souk Ahras Meteorological Station Data). Data sampling Sampling was conducted between March and July during the years 2020–2023. We carried out a systematic search for blackbird Turdus merula nests within the Machroha forests (Souk Ahras province, northeast Algeria). Regular field visits were conducted every three days at most, including consecutive and crepuscular surveys, to locate nests and describe the surrounding habitat. The blackbird is a very common passerine belonging to the Turdidae family, recognized by its powerful, flute-like song and sharp alarm calls. Its average territory ranges between 0.2 and 0.5 ha, which facilitated the targeted mapping of breeding pairs using the IPA (Individual Placement Assessment) method. Nests were located through systematic searches in the study area, focusing on areas with active blackbird presence. Each nest was checked at 3–4-day intervals throughout the breeding season to monitor activity. To avoid double-counting, nests were marked with a unique code, and GPS coordinates were recorded for each nest. Only nests with distinct locations were included in analyses (Al Kadiri and Al-Husari 2026). Nest height was measured from the base of the nest to the ground. Nest internal diameter (NID) and depth (ND) were measured using a caliper (Figure 1). The “clutch size” was defined as the total number of eggs laid in a nest during a single breeding attempt. Only complete clutches were considered, and partial or abandoned clutches were excluded from analyses. The “hatching success” was recorded as a binary variable for each nest: 1 if at least one egg hatched, and 0 if no eggs hatched, reflecting whether a nesting attempt produced any hatchlings. The “fledging success” or “number of chicks” refers to hatched chicks alive at day 5 post-hatching, as this represents the early survival stage before potential predation or abandonment. These measurements followed standard protocols for passerine nest studies (Hansell 2000, Furness 2025). Data Analyses and processing All statistical analyses were conducted in R software (R version 4.3.3). Data were first screened for completeness and consistency. Descriptive statistics (mean ± standard deviation, median, range) were calculated for nest structural variables and reproductive parameters using base R functions and the “dplyr” package. All graphical outputs were produced using the “ggplot2” package. Statistical significance was set at α = 0.05. Normality of continuous variables was assessed using the Shapiro–Wilk test. As several variables did not meet parametric assumptions, non-parametric tests were applied when appropriate. Inter-annual variation and differences between forest sections were evaluated using Kruskal–Wallis tests, followed by pairwise Wilcoxon rank-sum tests for post hoc comparisons. When assumptions were met, linear models were applied. Associations among nest architectural traits were examined using Spearman’s rank correlation coefficients computed with the “Hmisc” package. Correlation matrices were used to assess the strength and direction of relationships among structural variables. To investigate multivariate patterns of nest architecture, Principal Component Analysis (PCA) was performed on standardized variables using the “FactoMineR” package. Eigenvalues, percentage of variance explained, and variable loadings were extracted to interpret the contribution of each trait to principal components. PCA visualizations were generated using “ggplot2” and “factoextra”. To explore potential grouping patterns among nests, k-means clustering (k = 2) was applied to PCA scores (Dim.1 and Dim.2). The optimal number of clusters (k = 2) was determined based on the elbow method and supported by average silhouette width. Cluster membership was summarized and compared across forest sections to evaluate structural differentiation. Reproductive success was analyzed using Generalized Linear Models (GLMs) implemented with the “stats” package. Depending on the response variable distribution, appropriate error structures were specified. Hatching success was defined as a binary outcome at the nest level (success versus failure) and was therefore analyzed using logistic regression with a binomial error distribution. The number of chicks recorded at day 5 after hatching was treated as a count variable and analyzed using Poisson regression. For Poisson models of chick counts, model assumptions were checked using the dispersion statistic (residual deviance / residual degrees of freedom) to detect potential over-dispersion. A dispersion statistic >1.5 indicates over-dispersion, in which case a negative binomial (NegBin) model was fitted as an alternative. Because some nests produced no chicks, the potential presence of zero inflation was also examined. Model adequacy was assessed through residual diagnostics and goodness-of-fit evaluation. Spatial autocorrelation was evaluated using Moran’s I implemented in the R package “sf” and “spdep”. Spatial weights were based on a k-nearest neighbor approach (k = 4), and significance was assessed using permutation tests with 999 simulations. Nest coordinates (latitude and longitude, WGS84) were used to define spatial locations. Breeding performance of blackbird A total of 76 nests of Blackbird Turdus merula were recorded in the Machroha forest between 2020 and 2023, with 43 nests in Razgoun and 33 nests in Mghassel. Descriptive statistics of nest measurements and breeding outputs are summarized in Table 1. Nest height ranged from 0.8 to 5.3 m (mean ± SD = 1.88 ± 0.69 m), nest diameter from 8.5 to 14.5 cm (12.05 ± 1.55 cm), and nest depth from 3.0 to 7.5 cm (4.97 ± 1.01 cm). The number of eggs per nest ranged from 2 to 5 (3.57 ± 0.75), while the number of chicks varied from 0 to 4 (2.21 ± 1.65). Shapiro-Wilk tests indicated that none of the nest measurements or breeding variables were normally distributed across the entire dataset (Nest Height: W = 0.695, p < 0.001; Nest Internal Diameter: W = 0.957, p = 0.012; Nest Depth: W = 0.958, p = 0.013; Clutch size: W = 0.849, p < 0.001; Number of chicks: W = 0.776, p < 0.001). When tested by site, nest height deviated from normality in both Razgoun (W = 0.734, p < 0.001) and Mghassel (W = 0.882, p = 0.002). Nest diameter was normally distributed in Mghassel (W = 0.957, p = 0.207) but slightly non-normal in Razgoun (W = 0.940, p = 0.026). Nest depth was approximately normal in Razgoun (W = 0.972, p = 0.378) but not in Mghassel (W = 0.915, p = 0.013). Breeding output (clutch size and number of chicks) significantly deviated from normality in both sites (Clutch size – Razgoun: W = 0.850, p < 0.001; Mghassel: W = 0.838, p < 0.001; number of chicks – Razgoun: W = 0.779, p < 0.001; Mghassel: W = 0.772, p < 0.001). Overall, the descriptive statistics show moderate variability in nest architecture and breeding output, providing a solid basis for further comparative and modeling analyses (Table 1). Inter-annual and forest sections nest variation Comparison of nest architecture and breeding output between the two forest sections (Razgoun and Mghassel) using Wilcoxon rank-sum tests showed that nest height did not differ significantly between sites (W = 724.5, p = 0.879). However, nest diameter and nest depth were significantly different, with Razgoun nests being slightly smaller in diameter (W = 512, p = 0.038) and shallower (W = 462, p = 0.009) than Mghassel nests. In contrast, breeding parameters, including the clutch size (W = 756, p = 0.601) and number of chicks (W = 689, p = 0.826), did not differ significantly between sites. These results suggest that while minor differences in nest architecture exist between Razgoun and Mghassel, breeding success was comparable across the two forest sections. Nest height varied significantly among years (χ² = 15.68, df = 3, p = 0.001). Post-hoc pairwise comparisons (Wilcoxon tests with Bonferroni correction) indicated that nest height in 2020 was significantly lower than in 2021 (p = 0.008), 2022 (p = 0.018), and 2023 (p = 0.034). Other year-to-year differences were not significant. Nest diameter showed a modest but significant difference across years (χ² = 8.31, df = 3, p = 0.040). Pairwise comparisons suggested no individual year pairs were significantly different after Bonferroni correction (all p > 0.05). Nest depth also varied significantly among years (χ² = 14.63, df = 3, p = 0.002). Post-hoc tests revealed that nests in 2020 were shallower than in 2022 (p = 0.011) and 2023 (p = 0.003). Differences between other years were not significant. Number of eggs per nest (clutch size) did not differ significantly among years (χ² = 3.40, df = 3, p = 0.333), so no post-hoc tests were required. Number of chicks per nest varied significantly across years (χ² = 21.25, df = 3, p < 0.001). Post-hoc comparisons showed that nests in 2020 had fewer chicks than in 2021 (p = 0.00072), 2022 (p = 0.0089), and 2023 (p = 0.0010). Other comparisons between years were not significant. These results indicate that while some nest structural characteristics and breeding output varied between years, overall breeding performance remained relatively stable, with the most notable differences observed between 2020 and later years. Blackbird nests spatial distribution Spatial autocorrelation of nest characteristics and reproductive output was assessed using Moran’s I statistics. Spatial weights were defined using a k-nearest neighbor approach (k = 4) based on nest coordinates, and significance was tested with randomization. Moran’s I statistics indicated a significant positive spatial autocorrelation for nest depth (I = 0.192, p = 0.002), suggesting that deeper nests tend to cluster within the forest. Nest height (I = 0.089, p = 0.062) and nest diameter (I = 0.066, p = 0.136) showed weak, non-significant clustering, while clutch size (I = -0.106, p = 0.899) and number of chicks (I = -0.095, p = 0.868) were randomly distributed, indicating that reproductive output is independent of spatial location within the Machroha forest (Figure 2). Nest Architecture × Breeding Success relationship We explored whether nest architecture influenced breeding output in blackbird nests. Spearman’s rank correlation tests indicated that nest height was positively associated with the number of chicks per nest (rho = 0.29, p = 0.011), while nest diameter and depth were not significantly correlated with the number of chicks (p > 0.05). None of the nest dimensions were significantly correlated with the number of eggs per nest (p > 0.3 for all variables). A Poisson regression model further confirmed these results. Nest height was the only significant predictor of the number of chicks (β = 0.261 ± 0.086, z = 3.03, p = 0.002), whereas diameter (β = 0.007, p = 0.903) and depth (β = 0.033, p = 0.708) had no significant effect. The model explained a portion of the variation in chick numbers (residual deviance = 132.97, AIC = 297.03). The residual deviance relative to residual degrees of freedom (132.97 / 72 ≈ 1.85) indicated moderate over-dispersion. A negative binomial model was also fitted and produced qualitatively similar results, confirming the robustness of the findings These findings suggest that taller nests may provide a slight advantage for chick survival or development, whereas other structural characteristics of nests (diameter and depth) do not appear to influence breeding success. Overall, nest architecture seems to play a modest role in determining breeding output in this population. Multivariate analyses of nests architecture Spearman correlation analysis (n = 76 nests) revealed that most nest architectural traits were largely independent. Nest height was not significantly correlated with diameter (ρ = −0.041, p = 0.728) or depth (ρ = −0.014, p = 0.901). In contrast, nest diameter and depth showed a strong and significant positive correlation (ρ = 0.524, p < 0.001), indicating that wider nests tend to be deeper (Figure 3). Principal Component Analysis (PCA) summarized the structural variation of nests into two dominant axes explaining 84.09% of the total variance (Figure 4). The first principal component (PC1) accounted for 50.94% of the variance and was strongly associated with nest diameter (loading = 0.870) and nest depth (loading = 0.870), representing overall nest size (Table 2). The second principal component (PC2), explaining 33.15% of the variance, was primarily driven by nest height (loading = 0.992), reflecting vertical structural variation independent of nest width and depth (Table 3). Clustering analysis based on PCA scores identified two main groups of nests. Cluster 1 included 22 nests from Mghassel and 22 from Razgoun, whereas Cluster 2 comprised 11 nests from Mghassel and 21 from Razgoun. The distribution of nests across clusters indicates partial overlap between forest sections, suggesting that although nest architecture exhibits measurable structural variation, site-related differentiation remains moderate rather than strictly segregated (Table 4). Discussion Breeding performance of blackbird The breeding performance observed in Machroha forest aligns with the reproductive range reported across Mediterranean and temperate European populations of Turdus merula . Clutch size stability across years is consistent with patterns documented in Spain, Italy, and southern France, where egg-laying investment tends to be conservative, while variation more frequently occurs during the nestling phase (Ibáñez-Álamo et al. 2015, Senar et al. 2017, Capilla-Lasheras et al. 2017). Across the Mediterranean basin, reproductive output in blackbirds is strongly influenced by seasonal rainfall and invertebrate availability (Both et al. 2010, Pearce-Higgins et al. 2015). The generally stable productivity observed in Machroha suggests that this forest currently provides adequate trophic conditions during the breeding season. Comparable clutch sizes have been reported in North African urban and semi-natural populations (Djemadi et al. 2015), indicating that northeastern Algerian habitats fall within the species’ broader Mediterranean reproductive envelope. By situating the Machroha population within this gradient, these findings reinforce the notion that Maghreb populations are ecologically comparable to southern European ones, despite differing climatic intensity. Nest architectural plasticity Structural differences in nest architecture between Razgoun and Mghassel did not translate into differences in reproductive success. This pattern reflects the well-documented architectural plasticity of Turdus merula (Mainwaring et al. 2014, Deeming and Mainwaring 2015). Nest construction in passerines responds to microhabitat structure, material availability, and exposure rather than directly determining breeding output. In Mediterranean woodlands, blackbirds exhibit high behavioral flexibility in nest-site selection, adjusting to shrub density, canopy cover, and human disturbance (Ibáñez-Álamo and Soler 2010, Møller et al. 2014). The absence of demographic divergence between forest sections suggests functional habitat equivalence rather than ecological segregation. Similar findings have been reported in Italian oak forests and Spanish Mediterranean scrublands, where microhabitat variation modifies nest traits without affecting fledging success (Grieco 2012, Senar et al. 2017). This indicates that nest architectural variability in Machroha reflects environmental accommodation rather than adaptive differentiation. Nest inter-annual and forest sections variation Temporal variation in nest structure and chick production suggests environmental modulation of breeding conditions. Mediterranean passerines are highly sensitive to interannual climatic variability, particularly spring rainfall anomalies and temperature extremes (Both et al. 2010, Peñuelas et al. 2017). Such conditions primarily affect food abundance during the nestling stage rather than egg production. The stability of clutch size alongside variation in chick production supports this mechanism. Similar decoupling between laying effort and fledging success has been documented in Iberian blackbird populations during drought years (Ibáñez-Álamo et al. 2015) and in French long-term monitoring programs (Charmantier et al. 2018). These studies demonstrate that reproductive bottlenecks often occur post-hatching. The apparent recovery in subsequent years suggests short-term ecological stress rather than structural habitat degradation, reflecting the resilience characteristic of generalist passerines occupying Mediterranean systems subject to climatic oscillations (Jiguet et al. 2019). Spatial distribution and forest ecosystem regulation The spatial autocorrelation revealed that reproductive output was randomly distributed across the study area, as neither clutch size nor the number of chicks showed significant spatial autocorrelation. This suggests that breeding performance is not spatially structured within the Machroha forest. In territorial birds such as the blackbird, nest dispersion is often regulated by conspecific territorial mechanisms rather than fine-scale habitat patchiness (Snow and Snow 2010, Senar et al. 2017). Although reproductive parameters were spatially random, nest depth showed a significant positive spatial autocorrelation, indicating that similar nest construction characteristics tend to cluster locally. This pattern may reflect local similarities in vegetation structure or nest-supporting substrates within the forest. Random spatial patterns in reproductive output generally suggest relatively homogeneous habitat quality. Comparable findings have been reported in mixed deciduous forests in France and Germany, where blackbirds establish evenly spaced territories independent of micro-scale vegetation heterogeneity (Møller et al. 2014). Together, these results support the interpretation that the Machroha forest functions as a continuous breeding matrix rather than a mosaic of uneven-quality habitat patches. Blackbird nests traits in Machroha forest Nest height appears to play a modest yet significant role in chick survival. Vertical placement is widely recognized as a determinant of nest predation risk in passerines (Martin and Roper 1988, Mainwaring et al. 2014). In Mediterranean ecosystems, elevated nests may reduce vulnerability to terrestrial predators while improving ventilation under warm spring conditions. Studies from Spain and Italy have shown that blackbirds nesting higher in vegetation experience lower predation rates, particularly in shrub-dominated landscapes (Ibáñez-Álamo and Soler 2010, Capilla-Lasheras et al. 2017). Additionally, nest microclimate buffering becomes increasingly important under rising Mediterranean temperatures (Deeming and Mainwaring 2015). The independence of nest height from overall nest size suggests that vertical placement represents a behavioral decision rather than a structural by-product. However, reproductive success remains multifactorial, shaped by interacting ecological drivers. The strong association between nest diameter and depth reflects coordinated construction patterns, a phenomenon widely observed across passerine species (Mainwaring et al. 2014). Nest dimensions are often constrained by material properties, biomechanical stability, and energetic investment rather than directly optimized for reproductive output (Deeming and Reynolds 2015). The identification of two principal axes—overall nest size and vertical placement—suggests that Machroha blackbirds modulate nest architecture along predictable ecological gradients. Similar structural organization has been documented in European thrush populations, reinforcing the generality of this architectural framework. Breeding ecology data from North Africa remain comparatively scarce relative to European datasets (Djemadi et al. 2015, Zeraoula et al. 2015, El-Hassani et al. 2021). By providing multi-year reproductive and architectural data from a semi-natural forest system, this study contributes valuable regional insight. Integrating Maghreb populations into Mediterranean comparative analyses is particularly important under projected climate warming scenarios, as southern populations may serve as early indicators of thermal stress effects on breeding phenology and success (Peñuelas et al. 2017, Jiguet et al. 2019). Conservation implication in northeast Algeria The overall stability of breeding parameters, combined with spatial homogeneity and architectural plasticity, indicates that Machroha forest currently supports a viable breeding population of Turdus merula. The sensitivity of chick survival to nest height suggests that vegetation structure—particularly shrub layer complexity—may be important for maintaining reproductive success. Given ongoing Mediterranean forest pressures, including fragmentation and drought intensification, continued monitoring will be critical. Long-term datasets linking breeding success with climatic variables would allow stronger inference regarding environmental drivers and population resilience. Acknowledgment The authors of this article are grateful to all volunteers who participate during the sampling. We are also gratefully acknowledge the Ministère de l’enseignement supérieur et de la recherche scientifique (MESRS, Algérie) and the Direction de la Recherche Scientifique et du Développement Technologique (DGRSDT, Algérie) for their moral support. Funding statements This study was conducted without any external funding or financial support from public, commercial, or not-for-profit sectors. Declaration of competing interest The authors declare no conflict of interest. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Data availability statement: All data that support the findings of this study are included within the article. CrediT authorship contribution statement B.A: Conceptualization, Data collection, writing-original draft. B.M: Conceptualization, Data Analysis, writing-original draft. A.A.M: Conceptualization, Data Analysis, review-original draft. All authors have read and agreed to the published version of the manuscript. Declaration of generative AI During the editing of this manuscript, the authors used responsibly ChatGTP to improve the fluency and coherence of the text. After using this tool/service, the author reviewed and edited the content as needed and takes full responsibility for the content of the published text. References Al Kadiri, M. A., and M. H. 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Keywords 1.020: behavioral ecology 1.100: population ecology 1: field of ecology 2.180: statistical method 2: topic 3.050: birds 3: organisms blackbird breeding chicks’ survival machroha forest nest architecture spatial distribution Authors Affiliations Abdelhak Boucif Université 8 Mai 1945 Guelma View all articles by this author Mouslim Bara 0000-0003-3818-424X [email protected] View all articles by this author A. Mohammad Al Kadiri Yarmouk University View all articles by this author Metrics & Citations Metrics Article Usage 171 views 77 downloads .FvxKWukQNSOunydq8rnd { width: 100px; } Citations Download citation Abdelhak Boucif, Mouslim Bara, A. Mohammad Al Kadiri. Nest architectural traits and reproductive success of blackbird Turdus merula in a Mediterranean forest: implications for population dynamics in northeastern Algeria. Authorea . 01 April 2026. 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