Water level manipulations in human-made impoundments drive species- and guild-specific responses in wetland bird communities

Water level manipulations in human-made impoundments drive species- and guild-specific responses in wetland bird communities | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Water level manipulations in human-made impoundments drive species- and guild-specific responses in wetland bird communities Kiirsti C. Owen, Mark L. Mallory, Devin R. Zwaan, Nic R. McLellan, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-8889532/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract For over half a century, wildlife managers have constructed impoundments to offset wetland habitat loss across North America. As impoundments age, productivity often declines, and water-level drawdowns are commonly used to rejuvenate habitat and primary productivity and increase wildlife use, particularly targeting wetland bird communities. We evaluated the effectiveness of drawdowns in coastal impoundments of Atlantic Canada, where responses to management are poorly understood. From April–June 2021–2023, we used a replicated before–after–control–impact (BACI) design to assess bird occupancy and abundance at untreated, drawdown, and post-treatment wetlands using generalized additive and mixed-effects models. We also tested the response of aquatic macroinvertebrates to drawdown. Bird responses varied among foraging guilds and species. Shallow-water foragers, including aquatic ground predators and some dabbling ducks, increased during drawdown, whereas aquatic diving species declined. Following refilling, overall bird abundance increased significantly at treatment wetlands relative to controls. Aquatic macroinvertebrate abundance did not increase after drawdown, suggesting that bird responses were more strongly linked to changes other than standing prey biomass. These findings indicate that drawdowns can enhance wetland bird use but generate trade-offs among species with different functional traits and habitat requirements. Managing impoundments on a rotating drawdown schedule to maintain habitat heterogeneity at a landscape scale may help maximize biodiversity and support a broader range of wetland birds in Atlantic Canada. aquatic macroinvertebrates coastal impoundments drawdown habitat management waterfowl wetland senescence Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Wetlands, the transition zones between terrestrial and aquatic environments, provide critical ecosystem services and support rich biodiversity. These services include carbon sequestration, flood mitigation, water storage, and habitat for diverse wildlife (Mitsch and Gosselink 2007 , Mitsch et al. 2015 ). Despite their importance, over 50% of the world’s natural wetlands have been lost since the 1700s (Davidson 2014 , Fluet-Chouinard et al. 2023 ), with particularly severe losses in coastal regions where human settlement has historically concentrated (Mitsch and Gosselink 2007 , Barbier et al. 2011 ). Human-made wetlands, such as impoundments, are commonly constructed to offset wetland loss and compensate for some of the ecosystem services provided by natural wetlands, particularly habitat for waterfowl and other wetland wildlife (Keith 1961 ). Although impoundments can provide important wildlife habitat, managers have long observed declines in nutrient availability, changes in invertebrate communities, and reduced wildlife use as impoundments age (Kadlec 1962 , Baldassarre and Bolen 2006 , Demers 2021 , Rawal et al. 2026 ). This process, known as wetland senescence, occurs as static, human-controlled water levels promote vegetation succession and limit nutrient cycling, leading to reduced habitat quality and productivity over time (Fredrickson 1985 , Loder et al. 2018a , b ). Water-level drawdowns have been used since the mid-20th century as a management strategy to counteract wetland senescence and rejuvenate productivity in aging impoundments (Kadlec 1962 , Meeks 1969 ). Drawdowns temporarily expose wetland sediments to aerobic conditions, stimulate decomposition of accumulated organic matter, and reset plant communities, thereby increasing nutrient availability upon reflooding (Baldassarre and Bolen 2006 ). In many regions of North America, drawdowns have been associated with increased nutrient availability, macroinvertebrate production, and waterbird abundance, as well as shifts toward earlier successional vegetation communities (Kadlec 1962 , Meeks 1969 , Lumsden et al. 2015 , Schummer et al. 2021 ). Impoundments support a wide range of wetland wildlife, and drawdowns can create dynamic habitat conditions that benefit different groups of birds at different stages of water-level manipulation (Rundle and Fredrickson 1981, Kaminski et al. 2006 ). Shallow water and exposed mudflats during drawdown can provide foraging habitat for shorebirds and dabbling waterfowl, whereas refilled impoundments may favor diving species that require deeper water (Taft et al. 2002 ). Although drawdowns are often implemented to improve habitat conditions for waterfowl, they may also influence non-target species and overall bird community composition, highlighting the importance of evaluating both community-level and species-specific responses. In Atlantic Canada, coastal wetlands are particularly important for breeding, migrating, and overwintering birds along the Atlantic Flyway (Erwin 1996 ), yet these systems have experienced extensive historical loss. In the Maritime provinces, at least two-thirds of coastal wetlands were lost following European settlement as wetlands were dyked and drained for agriculture and development (Government of Canada 1991 , Butzer 2002 ). To compensate for these losses, Ducks Unlimited Canada and the Canadian Wildlife Service constructed numerous impoundments beginning in the mid-20th century (Loder et al. 2019 ), often on former coastal wetlands underlain by marine-derived clays and silts (van Proosdij et al. 2010 , Loder et al. 2018a ). These impoundments differ from those in other regions of North America because they occur on nutrient-poor, marine-derived soils, and evidence of wetland senescence has been documented through declining nutrients, altered macroinvertebrate communities, and reduced wildlife use (Loder et al. 2018b , Demers 2021 ). Despite widespread use of drawdowns elsewhere, there is little peer-reviewed research evaluating drawdown effects in coastal impoundments of Atlantic Canada, where ecological responses may differ from those observed in freshwater inland systems. Loder et al. ( 2019 ) found that freshwater impoundments built on marine-derived soils in the Nova Scotia – New Brunswick border region had generally higher nutrients than freshwater waterbodies managed for waterfowl in other areas of North America but were less productive than shallow wetlands in the Prairie Pothole Region. Moreover, most drawdown studies have focused on overwintering habitats in southern regions (e.g., Wiebe 1946 , Taft et al. 2002 ), leaving uncertainty about drawdown effects on breeding and migratory bird communities in northern coastal systems. Here, we used a Before-After-Control-Impact (BACI) design to evaluate the effects of water-level drawdowns on bird communities, focal species, and aquatic macroinvertebrates in coastal impoundments of southeastern New Brunswick. By integrating community-level, species-level, and mechanistic responses, we aimed to assess whether drawdowns function as an effective management tool in this region and to identify potential trade-offs among taxa. We hypothesized that water-level drawdowns alter bird use of impoundments by changing habitat structure and food availability. We predicted increased macroinvertebrate abundance and biomass following reflooding, leading to higher bird occupancy and abundance at post-treatment wetlands relative to pre-treatment conditions and control sites. We further predicted that responses would vary among species and foraging groups, with shallow-water foragers responding positively during drawdown and aquatic diving species responding negatively due to reduced water depth. Methods Study locations We monitored freshwater impoundments in southeastern New Brunswick, Canada (45.910, -64.306). Seven impoundments were selected for experimental drawdown treatment, each paired with at least one nearby unmanipulated impoundment serving as a control. Additional control sites occurred in clusters where no impoundments were selected for manipulation. In total, we monitored 19 impoundments (control: n = 12; treatment: n = 7; Figure 1; Appendix 1). Impoundments were selected based on accessibility, proximity to other impoundments, and recommendations from Ducks Unlimited Canada biologists and collaborating researchers. Assignment of treatment and control status occurred after collection of baseline data on birds, macroinvertebrates, and vegetation, and incorporated logistical constraints. All drawdowns were administered by Ducks Unlimited Canada. All impoundments were freshwater systems constructed on former coastal dykelands and occurred in pairs or clusters (Figure 1; Appendix 1). Each was bounded by an earthen berm with a water control structure allowing manipulation of water levels (Kelly et al. 1993). Surrounding land use included agriculture, forest, National Wildlife Areas, and rural properties. Impoundments were located near the Bay of Fundy, the Memramcook River, channelized ditches, or bogs, and were managed by Ducks Unlimited Canada or the Canadian Wildlife Service. We surveyed all impoundments at least once per week during three field seasons (early April - late September 2021–2023), spanning the breeding season and portions of spring and fall migration. In 2021, we collected pre-treatment data on wetland bird occupancy and abundance and macroinvertebrate abundance and biomass. Occupancy was defined as presence/non-detection, and abundance as counts of individuals per wetland. Macroinvertebrate biomass was measured as total dry mass per wetland per year. Water control structures (e.g., stop logs) were removed in late winter 2022, and wetlands were allowed to drain through the summer drawdown period (Figure 2). Structures were reinstalled in fall 2022, and impoundments refilled passively via precipitation and snowmelt over winter. Post-treatment data were collected in 2023. During drawdowns, water remained in borrow pits along impoundment margins. One treatment wetland failed to drain and refill fully and was excluded from analyses. All remaining treatment wetlands refilled to normal operating levels prior to 2023 surveys, therefore, we collected three years of monitoring at 19 wetlands: 2021 was monitored as pre-treatment, 2022 was monitored as 7 treatment and 12 controls, and 2023 was monitored as 7 post-treatment and 12 controls (with one treatment removed during analyses). Wetland bird surveys Bird surveys were conducted by one or two observers walking the perimeter of each impoundment and recording all birds seen or heard within wetland boundaries. Songbirds were recorded as presence/non-detection only, as they were not the focus of this study. Presence/non-detection of mammals, amphibians, and reptiles was also noted. Survey duration varied with wetland size and typically ranged from 30–75 minutes. At two sites, perimeter surveys were not feasible due to dense vegetation or closely adjacent impoundments. These sites were surveyed using spotting scopes from fixed vantage points. Survey methods were consistent within each wetland across years. Surveys began when light conditions allowed accurate visual identification of waterfowl (i.e., just before sunrise on clear days). Surveys were not initiated more than five hours after sunrise and were not conducted during rain or heavy fog. For adjacent impoundments separated by a center dyke, both observers walked the dyke simultaneously to reduce double-counting. For adjacent sites without a center dyke, observers coordinated via handheld radios to confirm bird movements between wetlands. Birds entering the wetland during surveys were counted only if observers were confident movements were unrelated to observer disturbance. Flyovers were excluded unless birds were actively interacting with the wetland (e.g., foraging swallows, hunting raptors). Flyovers were rare and unlikely to influence counts. At the start of each survey, observers recorded date, time, weather conditions (precipitation, wind, temperature), and disturbance (i.e., anything that might influence detection such as highway noise or passing trains). A standardized photograph was taken from the survey starting point to document seasonal vegetation change. Macroinvertebrate sampling Macroinvertebrates were sampled in late May of each year, coinciding with peak waterfowl nesting and brood-rearing periods (Schummer et al. 2021). Sampling followed methods outlined by Demers (2021) using a D-frame dip net. At each wetland, five randomly selected shoreline points were sampled annually using a standardized two-meter V-shaped sweep with three bottom-contact bounces. Samples were rinsed into sealable plastic bags using impoundment water. Macroinvertebrates >4 mm were sorted from debris and vegetation, identified to Order, counted, and preserved in ethanol. Abundance was calculated by pooling counts across all five samples into a single wetland-level estimate per year. In 2024, preserved samples were transferred to coffee filters, drained, and air-dried. Filters containing invertebrates were weighed to estimate biomass. Mean filter mass (1.96 g), calculated from three unused filters, was subtracted from all sample weights to estimate total macroinvertebrate biomass (g dry mass) per wetland per year. Additional site-level data We derived site-level vegetation metrics using Sentinel-2 Level-2A imagery accessed through the Copernicus Data Space Ecosystem Browser (Copernicus Data Space Ecosystem 2024). We calculated mean Normalized Difference Vegetation Index (NDVI; Pettorelli et al. 2005) for each site by month during the survey period. To reduce inter-site variation unrelated to treatment, we calculated relative NDVI by subtracting each site’s mean seasonal NDVI from monthly NDVI values. This standardized NDVI values relative to each site’s baseline greenness, where positive monthly values are greater and negative values are lesser that average greenness per site. Wetland area (km²) was extracted from the same imagery source. Statistical analyses Generalized additive models We used generalized additive mixed models (GAMMs) to test treatment effects and to examine temporal patterns in bird use of impoundments. Models were fit using the mgcv package in R (v1.9-3; Wood 2017). We used cubic regression splines (basis = "cr" ) with a fixed basis dimension of k = 4 to enhance interpretability and reduce overfitting. Seasonal patterns were modeled using a smooth term for ordinal date. To account for repeated surveys at the same wetlands, site was included as a random effect using a random-effect smooth ( bs = "re" ). Abundance models were fit using a negative binomial error distribution, while occupancy models used a binomial distribution with a logit link. The trplus package (v1.2-4; Delignette-Muller and Dutang 2015) was used to guide selection of appropriate error distributions. Model selection was based on Akaike’s Information Criterion (AIC), beginning with a global model and sequentially removing terms; models within ΔAIC < 2 were considered competitive. Estimated degrees of freedom (edf) were examined to distinguish linear (edf ≈ 1) from non-linear effects. We used a threshold of α = 0.05 for significance but report marginal significance at α = 0.10 to show general patterns. Global models for each species or species group included ordinal date, wetland area (km²), aquatic macroinvertebrate biomass (g), year, and treatment, with site included as a random effect. Treatment was included as both a main effect and, where supported by the data, as an interaction with ordinal date. For species with low sample sizes (e.g., Pied-billed Grebe Podilymbus podiceps and Sora Porzana carolina ), the treatment × date interaction was not estimable and was removed. Because detection probability declined later in the season, most analyses used early-season data (April–June). Relative NDVI was excluded due to strong collinearity with ordinal date (r > 0.7) and low seasonal variability during this period. Community-level response variables We assessed community-level bird responses using survey count data for all waterbird species. Songbirds were excluded because only presence/non-detection data were collected. In addition to analyzing the full bird community, we grouped species into three foraging guilds, Aquatic Surface Herbivores, Aquatic Diving Predators, and Aquatic Ground Predators, based on Avibase classifications (Lepage 2024; Appendix 2). These guilds represent ecologically meaningful groups and allowed inclusion of species with insufficient detections for species-level modeling. For swallows (four locally occurring species), we modeled occupancy using the full April–September dataset because detection remained high throughout the season due to their aerial foraging behavior. Swallows are aerial insectivores, a guild of conservation concern across North America (Birds Canada and Environment and Climate Change Canada 2024). BACI analyses for community and macroinvertebrate responses To explicitly test for Before–After–Control–Impact (BACI) effects, we conducted additional analyses examining whether changes through time differed between Treatment and Control wetlands (Chevalier et al. 2019). Site-level BACI We calculated site-level mean values for each response variable (total bird abundance, macroinvertebrate abundance, and macroinvertebrate biomass) for each period (Before = 2021; After = 2023). For each site, we computed the change through time (Δ = After − Before) and compared Δ values between Treatment and Control sites using linear models. Mixed-effects BACI models To incorporate all survey-level data, we fit mixed-effects BACI models of the form response (occupancy or abundance) by treatment (control or impact) with an interaction with period (before or after), where the Treatment × Period interaction represents the BACI framework. Site was included as a random effect to account for repeated measurements. For bird abundance, we additionally fit GAMMs including a Treatment × Period interaction and a smooth term for ordinal date to account for seasonal dynamics. Species-level response variables We modeled occupancy for focal species detected in ≥20% of surveys (13 species; Appendix 2), representing the core wetland bird community in the study area (Birds Canada and Environment and Climate Change Canada 2024). All species-level analyses used early-season data only (April–June) due to changes in detection probabilities after June. Macroinvertebrate data analysis To evaluate the effects of drawdowns on aquatic macroinvertebrates, we conducted both two-way factorial and one-way ANOVAs, depending on the comparison of interest. To align with the BACI design, we first used two-way ANOVAs with Treatment (Control vs. Impact) and Time (Before vs. After) as fixed factors, including the Treatment × Time interaction. Tukey HSD tests were used for post-hoc comparisons when main effects were significant (α = 0.05). Second, to compare macroinvertebrate responses among management categories (Untreated, Drawdown, Post-treatment), we conducted one-way ANOVAs for abundance and biomass, followed by Tukey HSD tests. Because our primary ecological interest was in whether drawdowns produced lasting effects, interpretation focused on comparisons between Untreated and Post-treatment wetlands. All analyses were conducted in R v4.4.1 (R Core Team 2024). Results Community-level response During 1,529 surveys conducted from April–September 2021–2023, we recorded 108 avian species using our focal impoundments. Analyses focused on birds for which abundance data were collected. Overall bird abundance did not respond strongly to the drawdown phase, although a potential weak negative effect was detected (β = -0.18, 95% CI = -0.14 to 0.59, p = 0.09). In contrast, overall bird abundance showed a significant positive response to the post-treatment stage, with higher abundance at post-treatment sites relative to untreated sites following reflooding (β = 0.37, 95% CI = -0.03 to 0.17, p < 0.001). For foraging guilds, Aquatic Ground Predators responded positively during the drawdown phase, whereas Aquatic Diving Predators showed significant negative responses during both the drawdown and post-treatment stages (Figure 4; Appendix 3). Aquatic Surface Herbivores exhibited reduced abundance during drawdown but increased abundance following refilling of the impoundments. Swallow occupancy was positively associated with the post-treatment stage, with higher site occupancy after refilling compared to untreated sites (Figure 3; Appendix 3). Site-level BACI analyses indicated greater increases in total bird abundance at Impact wetlands than at Control wetlands between the Before and After periods; however, responses varied substantially among sites. The estimated treatment effect was positive but marginal (β = 44.0, 95% CI = -5.69 to 93.8, p = 0.08), reflecting possible increases at a subset of Impact wetlands and little change at others. In contrast, mixed-effects BACI models incorporating all survey-level data revealed a strong positive treatment effect. The Treatment × Period interaction was significant, indicating that bird abundance increased at Impact wetlands relative to Controls following drawdown (β = 27.1, 95% CI = 13.9 to 40.3). There was no evidence of pre-treatment differences between Impact and Control wetlands, and Control sites showed little temporal change. Species-level response We examined species-level occupancy responses for nine waterfowl species, two waterbird species, and two songbird species (Appendix 4). During the drawdown phase, Blue-winged Teal ( Spatula discors ) and Green-winged Teal ( Anas carolinensis ) showed significant positive occupancy responses, whereas Ring-necked Duck ( Aythya collaris ), Wood Duck ( Aix sponsa ), Pied-billed Grebe, and Sora showed significant negative responses (Figure 4; Appendix 4). No species exhibited strong positive responses during the post-treatment stage. Ring-necked Duck and Pied-billed Grebe showed reduced occupancy following impoundment refilling relative to untreated sites. Swamp Sparrow ( Melospiza georgiana ) showed a weak positive post-treatment response, consistent with patterns observed for the Swallow group, although parameter estimates were small (Figure 4; Appendices 2 and 3). Macroinvertebrate response Site-level and mixed-effects BACI analyses indicated contrasting macroinvertebrate responses between Control and Treatment wetlands (Figure 5). Macroinvertebrate abundance increased at Control wetlands between 2021 and 2023, whereas Treatment wetlands exhibited a significantly smaller change through time (BACI difference = -112.2, 95% CI = -195.0 to -29.1, p = 0.01). Dry biomass showed a similar but weaker pattern, with reduced or delayed increases at Treatment wetlands relative to Controls (BACI difference = -0.218 , 95% CI = -0.459 to 0.022, p = 0.07). Discussion We found that overall bird abundance tended to increase in coastal impoundments following drawdown treatment, although responses varied among taxa, foraging groups, and individual wetlands. These results indicate that water-level manipulation can influence a broader suite of wildlife than the waterfowl typically targeted by impoundment management, including species of conservation concern. As such, conservation managers must consider not only target species but also the wider ecological consequences of water-level manipulation. Community-level responses We found support for the hypothesis that drawdowns increase bird abundance in the post-treatment phase, with a significant positive response detected when repeated surveys and site-level variation were accounted for. Although site-level BACI analyses indicated substantial heterogeneity among wetlands and were marginally non-significant, both GAMM analyses and mixed-effects BACI models consistently indicated increased bird use of drawdown wetlands following reflooding. Together, these results suggest that drawdowns can increase overall wetland bird abundance under favorable conditions, consistent with findings from other regions of North America where drawdowns are commonly used to rejuvenate impoundments (Suring and Knighton 1985 ). Responses among foraging guilds differed markedly during the drawdown phase. Aquatic Ground Predators responded positively, whereas Aquatic Surface Herbivores and Aquatic Diving Predators showed negative responses. These patterns are consistent with differences in habitat requirements among groups. Diving species typically forage in deeper water (> 25 cm; Taft et al. 2002 , Baschuk et al. 2012 ), whereas dabbling ducks prefer shallow water habitats (5–25 cm; Isola et al. 2000 , Taft et al. 2002 ). Shorebirds, which comprise a large proportion of the Aquatic Ground Predator group, preferentially forage in shallow water and exposed substrates created during drawdowns (Rundle and Fredrickson 1981). Bird abundance at post-treatment sites peaked in late April to mid-May, coinciding with peak shorebird migration through this portion of the Atlantic Flyway (Erwin 1996 , eBird 2024 ). If drawdowns are incorporated into future management plans, timing drawdowns to coincide with shorebird migration could enhance the value of these impoundments as stopover habitat. Migratory shorebird populations have declined by approximately 42% in Canada since 1980, with wetland and coastal habitat loss considered a major contributing factor (Birds Canada and Environment and Climate Change Canada 2024). Consequently, management actions that alter habitat availability during migration periods warrant careful consideration. During the post-treatment phase, Aquatic Diving Predators continued to show a negative response, although the magnitude was weaker than during drawdown. In contrast, Aquatic Surface Herbivores exhibited a positive post-treatment response, with increased abundance of dabbling ducks, particularly American Black Duck ( Anas rubripes ) and Mallard ( A. platyrhynchos ), following refilling. We did not detect corresponding changes in occupancy for these two species, suggesting that drawdowns influenced the intensity of site use rather than site selection. This distinction highlights the importance of considering both occupancy and abundance metrics when evaluating habitat management outcomes. Occupancy by swallows increased during the post-treatment phase, indicating that refilled impoundments may provide improved habitat for aerial insectivores. Most drawdown research has focused on waterfowl, yet wetlands support a wide range of taxa for foraging, nesting, and migration (Griffin 1982 , Cooper and Campbell 1997 ). To our knowledge, this is the first examination of drawdown effects on aerial insectivores. Previous work in the Chignecto Isthmus identified impoundments as important swallow roosting habitat (Saldanha 2016 , Fensore 2024 ), and the positive post-treatment response observed here may reflect increased availability of emergent insects following reflooding. Because macroinvertebrate sampling only occurred once per season and may have missed short-lived emergence pulses, future research should explicitly examine emergent insect dynamics and aerial prey availability following drawdowns. Species-level responses Species-level responses were variable but generally consistent with community-level patterns. Species-level results were interpreted cautiously and were primarily used to identify directional responses consistent with broader community-level trends, rather than to infer precise species-specific effect sizes. Several species, including Pied-billed Grebe, Sora, Ring-necked Duck, and Wood Duck, responded negatively during the drawdown phase. This was likely due to reduced water depth or overall wetland area. Wood Duck, for example, have been reported to forage at depths of 19–40 cm (Drobney and Fredrickson 1979) and reduced water levels may limit suitable foraging habitat. Sora densities have been reported to be similar between drawdown and high-water sites elsewhere (Baschuk et al. 2012 ), suggesting that factors beyond food availability, such as vegetation structure or habitat configuration, may influence their response to drawdown. In contrast, Green-winged Teal and Blue-winged Teal showed positive occupancy responses during drawdown, consistent with their reliance on shallow water and mudflat habitats (Bellrose 1980 ). Although no species exhibited strong positive occupancy responses during the post-treatment phase, exploratory analyses indicated increased abundance of American Black Duck, Mallard, and Green-winged Teal following refilling. Macroinvertebrate responses We did not find support for the hypothesis that drawdowns increased aquatic macroinvertebrate abundance or biomass within one year of refilling. Instead, both metrics were lower at treatment wetlands relative to controls, despite increased bird abundance. Similar outcomes have been reported elsewhere, where water-level manipulation reduced macroinvertebrate abundance following refilling (McEwen and Butler 2009), although other studies have documented increased macroinvertebrate abundance or biomass in wetlands following water-level changes (Anderson and Smith 2000, Schummer et al. 2021 ). A drawdown study conducted near our project area reported increased nutrient availability following drawdown but, similar to our own results, the study found lower macroinvertebrate abundance and biomass in treatment wetlands compared to controls (Hanson 1993 ), suggesting that recovery of macroinvertebrate communities may lag behind nutrient responses. Although some treatment sites in our study exhibited higher macroinvertebrate counts or biomass, most showed negative responses. Because macroinvertebrates were sampled once per season in late May, it is possible that recovery occurred later in the season or that pulses in abundance were missed due to a single sampling period per season. However, previous work in local wetlands found limited seasonal variation in macroinvertebrate abundance and biomass (Pollet et al. 2026 ), suggesting that timing alone is unlikely to fully explain observed patterns. Recommendations Responses by bird and macroinvertebrate communities to water-level drawdowns were mixed, highlighting the importance of aligning management actions with clearly defined conservation objectives. In Atlantic Canada, wildlife managers should consider which species or functional groups are being targeted before implementing drawdowns, as this management action benefitted some taxa (e.g., Green-winged Teal, Blue-winged Teal, swallows, Aquatic Surface Herbivores, and Aquatic Ground Predators) while negatively affecting others (e.g., Ring-necked Duck, Pied-billed Grebe, Sora, Wood Duck, and Aquatic Diving Predators). In addition, some groups responded positively only during the drawdown phase and not after refilling, indicating that benefits may be temporally limited and that timing is crucial. Given these trade-offs, we recommend managing impoundments on a rotating drawdown schedule, whereby some wetlands remain at normal operating levels while others undergo drawdown. This approach would allow managers to provide a mosaic of habitat conditions that support a broader range of wetland birds, including species with differing water-depth requirements (Rundle and Fredrickson 1981, Taft et al. 2002 ). Because impoundments in Atlantic Canada frequently occur in clusters, manipulating only one impoundment per cluster at a time may be particularly effective for increasing habitat heterogeneity at the landscape scale. Habitat heterogeneity is a well-established driver of biodiversity (MacArthur and MacArthur 1961 ), particularly at the landscape scale in heavily-modified habitats or agroecosystems (Fahrig et al. 2015 , Wilson et al. 2017 , de Zwaan et al. 2022 , 2024 ), and may help balance competing habitat needs among wetland bird communities. Although this study focused on short-term responses to a single year of drawdown and refilling, longer-term monitoring would improve understanding of how drawdowns influence wetland productivity and wildlife use over time. Continued monitoring of impoundments post-drawdown would be particularly valuable for evaluating delayed or cumulative responses in macroinvertebrate communities and bird use during the early breeding and migration period (April–June). Longer-term data would also help clarify how drawdowns interact with processes of wetland senescence, which previous research suggests may recur within five to seven years after impoundment construction in this region (Loder et al. 2018b , Demers 2021 ). Conclusion Water-level manipulation has long been used as a tool to improve habitat conditions in managed impoundments, yet its ecological consequences extend beyond waterfowl to a diverse array of wetland wildlife. Our results demonstrate that drawdowns can increase overall bird abundance in coastal impoundments of Atlantic Canada, while simultaneously generating trade-offs among species and functional groups. These findings highlight that drawdowns are not a universally beneficial management action, but rather one that reshapes habitat availability in ways that benefit some taxa while negatively influencing others. Recognizing and managing these trade-offs is critical for effective wetland stewardship. Strategies that promote spatial and temporal heterogeneity, such as rotating drawdowns among clustered impoundments, may allow managers to maximize biodiversity and support a wider range of wetland birds through time and space. By integrating community-level responses, species-level patterns, and mechanistic insights from macroinvertebrate dynamics, this study provides a regionally relevant framework for evaluating and refining drawdown-based management in coastal impoundments of Atlantic Canada. Declarations Acknowledgements Funding and support for this project was provided by a Mitacs Accelerate award to K. Owen (IT20776), Ducks Unlimited Canada, New Brunswick Wildlife Trust Fund, Nova Scotia Habitat Conservation Fund (contributions from hunters and trappers), Acadia University, University of New Brunswick, and Wildlife Habitat Canada. We thank field technicians Hannah Drake, Sarah Neima, Emily Peacock, Ruby Schweighardt, Fawn Maika, and Joel Eckerson, as well as several volunteers. We thank Al Hanson, Graham Forbes, Laura Tranquilla, and Tom Beckley for comments throughout the project, and Myriam Barbeau, Chris Edge, Wendy Monk, and Kate Sherren for additional comments on a final draft. Finally, we thank reviewers for their insights that helped improve our manuscript. Funding This work was supported by funding from a Mitacs Accelerate award to K. Owen (IT20776), Ducks Unlimited Canada, New Brunswick Wildlife Trust Fund, Nova Scotia Habitat Conservation Fund (contributions from hunters and trappers), Acadia University, University of New Brunswick, and Wildlife Habitat Canada. Competing Interests The authors have no relevant financial or non-financial interests to disclose. Author Contributions All authors contributed to study conception and design. Kiirsti Owen completed data collection, analysis, and wrote the manuscript. All authors provided comments on the manuscript and approved the final version Data Availability The datasets generated during this study are available from the corresponding author on reasonable request. References Baldassarre GA, Bolen EG (2006) Waterfowl Ecology and Management. 2 nd Edition. John Wiley & Sons. New York, NY, USA Barbier EB, Hacker SD, Kennedy C, Koch EW, Stier AC, Silliman BR (2011) The value of estuarine and coastal ecosystem services. 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Ecol Appl 29:e01838. https://doi.org/10.1002/eap.1838 Clipp HL, Peters ML, Anderson JT (2017) Winter waterbird community composition and use at created wetlands in West Virginia, USA. Scientifica 2017: 1730130. https://doi.org/10.1155/2017/1730130 Cooper JM, Campbell W (1997) Surveys of selected and traditional Black Tern ( Chlidonias niger ) colonies in British Columbia in 1996. Colonial Waterbirds 20:574 – 581. https://doi.org/10.2307/1521613 Copernicus Data Space Ecosystem (2024) Copernicus Data Space Ecosystem Browser . European Space Agency. https://dataspace.copernicus.eu/browser Accessed on 30 January 2024 Davidson NC (2014) How much wetland has the world lost? Long-term and recent trends in global wetland area. Mar Freshwater Res 65:934 – 941. https://doi.org/10.1071/MF14173 Delignette-Muller ML, Dutang C (2015) “fitdistrplus: An R Package for Fitting Distributions.” J Stat Softw 64:1–34. https://doi.org/10.18637/jss.v064.i04 Demers JASD (2021) Aquatic ecosystem senescence of wetland impoundments in the Upper Bay of Fundy, Atlantic Canada. M.Sc. Thesis, Mount Allison University de Zwaan DR, Alavi N, Mitchell GW, Lapen DR, Duffe J, Wilson S (2022) Balancing conservation priorities for grassland and forest specialist bird communities in agriculturally dominated landscapes. Biol Conserv 265:109402. https://doi.org/10.1101/2021.08.05.455200 de Zwaan DR, Hannah KC, Alavi N, Mitchell GW, Lapen DR, Duffe J, Wilson S (2024) Local and regional‐scale effects of hedgerows on grassland‐and forest‐associated bird populations within agroecosystems. Ecol Appl 34:e2959. https://doi.org/10.1002/eap.2959 Drobney RD, Frederickson LH (1979) Food selection by Wood Ducks in relation to breeding status. J Wildl Manage 43:109 – 120. https://doi.org/10.2307/3800641 eBird. 2024. eBird Basic Dataset . Cornell Lab of Ornithology, Ithaca, NY. https://ebird.org. Accessed 20 August 2024 Erwin RM (1996) Dependence of waterbirds and shorebirds on shallow-water habitats in the mid-Atlantic coastal region: an ecological profile and management recommendations. Estuaries 19:213-219. https://doi.org/10.2307/1352226 Fahrig L, Girard J, Duro D, Pasher J, Smith A, Javorek S, King D, Lindsay KF, Mitchell S, Tischendorf L (2015) Farmlands with smaller crop fields have higher within-field biodiversity. Agric Ecosyst Environ 200:219–234. https://doi.org/10.1016/j.agee.2014.11.018 Fensore SC (2024) Bank and Barn Swallow movement and roost site use patterns in eastern New Brunswick. Master’s Thesis, University of New Brunswick Fitzsimmons ON, Ballard BM, Merendino MT, Baldassarre GA, Hartke KM (2012) Implications of coastal wetland management to nonbreeding waterbirds in Texas. Wetlands 32:1057 – 1066. https://doi.org/10.1007/s13157-012-0336-2 Fluet-Chouinard E, Stocker BD, Zhang Z, Malhotra A, Melton JR, Poulter B, Kaplan JO, Klein Goldewijk K, Siebert S, Minayeva T, Hugelius G, Joosten H, Barthelmes A, Prigent C, Aires F, Hoyt AM, Davidson N, Finlayson CM, Lehner B, Jackson RB, McIntyre PB (2023). Extensive global wetland loss over the past three centuries. Nature 614:281-286. https://doi.org/10.1038/s41586-022-05572-6 Fredrickson LH (1985) Managed wetland habitats for wildlife: why are they important? In Water impoundments for wildlife: a habitat management workshop . North Central Forest Experiment Station, US Forest Service, St. Paul, MN, USA Fudge A (2019) Memory, place & change: a landscape narrative of the Tantramar Marshes. M.L.A. Thesis, University of Guelph. Government of Canada (1991) The federal policy on wetland conservation. Ministry of Environment. Griffin CR (1982) Ecology of Bald Eagles wintering near a waterfowl concentration. United States Department of the Interior – Special Scientific Report: Wildlife No. 247. Hanson A (1993) The effects of timing and duration of drawdown on impoundment productivity. Atlantic Region Cooperative Wetlands Research Program, Canadian Wildlife Service, Sackville, New Brunswick. Hapner JA, Reinartz JA, Fredlund GG, Leithoff KG, Cutright NJ, Mueller W (2011) Avian succession in small created and restored wetlands. Wetland s 31:1089 – 1102. https://doi.org/10.1007/s13157-011-0220-5 Isola CR, Colwell MA, Taft OW, Safran RJ (2000) Differences in habitat use of shorebirds and waterfowl foraging in managed wetlands of California’s San Joaquin Valley. Waterbirds 23:196-203. Kadlec JA (1962) Effects of a drawdown on a waterfowl impoundment. Ecology 43:267–281. https://doi.org/10.2307/1931982 Kaminski MR, Baldassarre GA, Pearse AT (2006) Waterbird responses to hydrological management of Wetlands Reserve Program Habitats in New York. Wildl Soc Bull 34:921-926. https://doi.org/10.2193/0091-7648(2006)34[921:WRTHMO]2.0.CO;2 Keith LB (1961) A study of waterfowl ecology on small impoundments in Southeastern Alberta. Wildl Monogr 6:3-88. Lepage D (2024) Avibase. Data Science and Technology, Birds Canada, Port Rowan, ON, Canada. https://avibase.bsc-eoc.org/ Accessed 15 April 2024 Loder AL, Mallory ML, Spooner I, McLellan NR, White C, Smol JP (2018a) Do rural impoundments in coastal Bay of Fundy, Canada sustain adequate habitat for wildlife? Wetlands Ecol Manage 26:213–230. https://doi.org/10.1007/s11273-017-9566-7 Loder AL, Mallory ML, Spooner IS, Turner M, McLellan NR (2018b) Nutrient availability reduced in older rural impoundments in coastal Bay of Fundy, Canada. Hydrobiologia 814:175–189. https://doi.org/10.1007/s10750-018-3535-x Loder AL, Spooner IS, McLellan NR, Kurek J, Mallory ML (2019) Water chemistry of managed freshwater wetlands on marine-derived soils in coastal Bay of Fundy, Canada. Wetlands 39:521–532. https://doi.org/10.1007/s13157-018-1101-y Lumsden HG, Thomas VG, Robinson BG (2015) Response of wild Trumpeter Swan ( Cygnus buccinator ) broods to wetland drawdown and changes in food abundance. Can Field-Nat 129:374–387. https://doi.org/10.22621/cfn.v129i4.1759 MacArthur RH, MacArthur JW (1961) On bird species diversity. Ecology 42:594 – 598. https://doi.org/10.2307/1932254 Meeks RL (1969) The effect of drawdown date on wetland plant succession. J Wildl Manage 33:817-821. https://doi.org/10.2307/3799312 Mitsch WJ, Bernal B, Hernandez ME (2015) Ecosystem services of wetlands. Int J Biodivers Sci Eco Services Mgmt 11:1 – 4. https://doi.org/10.1080/21513732.2015.1006250 Mitsch WJ, Gosselink JG (2007) Wetlands. John Wiley & Sons, New Jersey. Pettorelli NS, Olav Vik J, Mysterud A, Gaillard J-M, Tucker CJ, Stenseth NC (2005) Using the satellite-derived NDVI to assess ecological responses to environmental change. Trends Ecol Evo 20:503-510. https://doi.org/10.1016/j.tree.2005.05.011 Pollet IL, McLauchlan C, McLellan NR, Loder AL, Spooner I, Mallory ML (2026) Seasonal phenology, diversity, and relative abundance of macroinvertebrate waterfowl foods in a coastal wetland landscape in Maritime Canada. Wetlands Ecol Manage 34: 1. https://doi.org/10.1007/s11273-025-10102-y R Core Team (2023) R: A Language and Environment for Statistical Computing. R Foundation for Statistical Computing, Vienna, Austria. https://www.R-project.org/ Rawal P, Laaksonen T, Kačergytė I, Seimola T, Väänänen V-M, Lindén A (2026) Designing for diversity: Wetland ageing and habitat features at multiple scales influence the use of constructed wetlands by breeding waterfowl. Biol Conserv 314:111669. https://doi.org/10.1016/j.biocon.2025.111669 Rundle WD, Frederickson LH (1981) Managing seasonally flooded impoundments for migrant rails and shorebirds. Wildl Soc Bull 9:80-87. Saldanha S (2016) Foraging and roosting habitat use of nesting Bank Swallows in Sackville, NB. M.Sc. Thesis, Dalhousie University. Schummer ML, Easton KM, Hodges TJ, Farley EB, Sime KR, Coluccy JM, Tozer DC (2021) Response of aquatic macroinvertebrate density and diversity to wetland management and structure in the Montezuma Wetlands Complex, New York. J Great Lakes Res 47:875-883. https://doi.org/10.1016/j.jglr.2021.03.001 Stewart-Oaten A, Murdoch WW, Parker KR (1986) Environmental impact assessment: “Pseudoreplication” in time? Ecology 76:929 – 940. https://doi.org/10.2307/1939815 Suring LH, Knighton MD (1985) History of water impoundments in wildlife management. In Water impoundments for wildlife: a habitat management workshop . North Central Forest Experiment Station, US Forest Service, St. Paul, MN, USA. Taft OW, Colwell MA, Isola CR, Safran RJ (2002) Waterbird responses to experimental drawdown: implications for the multispecies management of wetland mosaics. J Appl Ecol 39:987-1001. https://doi.org/10.1046/j.1365-2664.2002.00763.x van Proosdij D, Lundholm J, Neatt N, Bowron T, Graham J (2010) Ecological re-engineering of a freshwater impoundment for salt marsh restoration in a hypertidal system. Ecol Eng 36:1314–1332. https://doi.org/10.1016/j.ecoleng.2010.06.008 Wiebe AH (1946) Improving conditions for migratory waterfowl on TVA impoundments. J Wildl Manage 10:4-8. https://doi.org/10.2307/3795805 Wilson S, Mitchell GW, Pasher J, McGovern M, Hudson MR, Fahrig L (2017) Influence of crop type, heterogeneity, and woody structure on avian biodiversity in agricultural landscapes. Ecol Indic 83:218–226. https://doi.org/10.1016/j.ecolind.2017.07.059 Wood S (2017) Generalized Additive Models: An Introduction with R , 2 nd edition. Chapman and Hall/CRC. Additional Declarations No competing interests reported. Supplementary Files Appendix.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 20 Apr, 2026 Reviews received at journal 10 Apr, 2026 Reviews received at journal 10 Apr, 2026 Reviewers agreed at journal 21 Mar, 2026 Reviews received at journal 20 Mar, 2026 Reviewers agreed at journal 20 Mar, 2026 Reviewers agreed at journal 27 Feb, 2026 Reviewers invited by journal 26 Feb, 2026 Editor assigned by journal 18 Feb, 2026 Submission checks completed at journal 17 Feb, 2026 First submitted to journal 15 Feb, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. Our growing team is made up of researchers and industry professionals working together to solve the most critical problems facing scientific publishing. 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-8889532","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":597978399,"identity":"3191f7d5-197d-437d-adbe-e0e392cb2941","order_by":0,"name":"Kiirsti C. Owen","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAAwElEQVRIiWNgGAWjYBACCWbGBhAlB+IceEC8lgQJY7CWBKK0gMkEhsQGCE0EkGxnbvv484dF+vywww+BttjJ6TYQ0CLNzNg8mydBInfj7TQDoJZkY7MDBLTIAbUwM4C0zE4AaTmQuI0YLYw/EiTSDWenfyBOC8hhDECHJchL5xBpi2Qz0GE8aRKGG6RzCg4kGBDhF4nzxx8z/rCpk5efnb75w4cKOzmCWuDAAKzSgFjlICDfQIrqUTAKRsEoGFEAAIYuPob8gtKKAAAAAElFTkSuQmCC","orcid":"","institution":"University of New Brunswick","correspondingAuthor":true,"prefix":"","firstName":"Kiirsti","middleName":"C.","lastName":"Owen","suffix":""},{"id":597978400,"identity":"ac3a5b5a-8d4b-48eb-b6fe-17680d9794f0","order_by":1,"name":"Mark L. Mallory","email":"","orcid":"","institution":"Acadia University","correspondingAuthor":false,"prefix":"","firstName":"Mark","middleName":"L.","lastName":"Mallory","suffix":""},{"id":597978402,"identity":"4b8fceb9-34f0-4942-9d4e-57ff1cf2536e","order_by":2,"name":"Devin R. Zwaan","email":"","orcid":"","institution":"Environment \u0026 Climate Change Canada, British Columbia","correspondingAuthor":false,"prefix":"","firstName":"Devin","middleName":"R.","lastName":"Zwaan","suffix":""},{"id":597978404,"identity":"6e44a524-0ce6-4a31-9907-15d7466ea672","order_by":3,"name":"Nic R. McLellan","email":"","orcid":"","institution":"Ducks Unlimited Canada","correspondingAuthor":false,"prefix":"","firstName":"Nic","middleName":"R.","lastName":"McLellan","suffix":""},{"id":597978406,"identity":"a1cde277-51ca-4031-aa99-2cb4903be20c","order_by":4,"name":"Joseph. J. Nocera","email":"","orcid":"","institution":"University of New Brunswick","correspondingAuthor":false,"prefix":"","firstName":"Joseph.","middleName":"J.","lastName":"Nocera","suffix":""}],"badges":[],"createdAt":"2026-02-16 04:23:46","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-8889532/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-8889532/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104402129,"identity":"ec8321e8-1dc1-428e-84d8-bb5a37baf958","added_by":"auto","created_at":"2026-03-11 12:14:24","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":532972,"visible":true,"origin":"","legend":"\u003cp\u003eMaps of study sites in southeast New Brunswick, Canada. Left: Map of 17 impoundments (control and treatment sites) in southeast New Brunswick, Canada. Bottom right: Smaller scale map providing a clearer view of eight impoundments (control and treatment sites) along the Missaquash River in southeast New Brunswick, Canada. Top right: Two impoundments (control sites) near the Memramcook River that are located outside the area of the larger map (Left). Black polygons outline impoundments selected as control sites and white polygons outline impoundments selected as treatment sites. Inset map shows the location of the study sites within the Canadian Maritimes (New Brunswick, Nova Scotia, and Prince Edward Island) with a black star showing the location of most impoundments included in the study (Left and Bottom right) and white star showing location of two additional control impoundments (Top right).\u003c/p\u003e","description":"","filename":"floatimage1.png","url":"https://assets-eu.researchsquare.com/files/rs-8889532/v1/55491382cafdc44ad8bf2276.png"},{"id":104401848,"identity":"d76b7665-bf0e-4ade-9862-5a5d71db541a","added_by":"auto","created_at":"2026-03-11 12:13:43","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":1365674,"visible":true,"origin":"","legend":"\u003cp\u003eDrone photos taken between 2021 – 2023 of two different freshwater impoundments included in this study on the Chignecto Isthmus, New Brunswick, Canada. Left: White Birch #3 impoundment before drawdown (top) and during drawdown (bottom). Right: Toler’s Flyway impoundment during drawdown (top) and post-drawdown (bottom). Photos: K. Owen.\u003c/p\u003e","description":"","filename":"floatimage2.png","url":"https://assets-eu.researchsquare.com/files/rs-8889532/v1/20ea233724fa60de0209257a.png"},{"id":103931940,"identity":"3d074649-20c7-4ed9-96a3-1b0410eaa5ad","added_by":"auto","created_at":"2026-03-04 16:41:28","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":127444,"visible":true,"origin":"","legend":"\u003cp\u003eSmoothed curves showing relationship between day of year (Day 100 = April 10th, Day 180 = June 28th, Day 250 = September 6th) and abundance of the three foraging groups (Aquatic Surface Herbivores, Aquatic Ground Predators, and Aquatic Diving Predators) and occupancy of one taxonomic group (Swallows). Data are from wetland bird surveys at impoundments of southeastern New Brunswick. Curves are coloured by treatment: green = Untreated (data pooled from all sites in 2021, n = 19, control sites only in 2022 and 2023, n = 12), orange = Drawdown or during treatment (2022 treatment sites only, n = 6), and blue = Post-treatment (2023 treatment sites only, n = 6). For the Swallow group, only “Untreated” and “Post-treatment” responses are displayed to ease interpretation (i.e., the “Drawdown” response has been removed). Note that the Y-axis scale varies by panel to visually maximize patterns.\u003c/p\u003e","description":"","filename":"floatimage3.png","url":"https://assets-eu.researchsquare.com/files/rs-8889532/v1/76ae9a0bc0d0d3544c0c2c4e.png"},{"id":104402363,"identity":"2d08bcd5-6959-419a-b812-08ff573b033d","added_by":"auto","created_at":"2026-03-11 12:15:10","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":228997,"visible":true,"origin":"","legend":"\u003cp\u003eEffect sizes for the influence of two treatment types on bird occupancy of 13 species: during treatment or drawdown (orange), and post-treatment (blue). Species-specific rates that differed significantly from zero (dashed grey line) are denoted with an asterisk (*). Points represent standardized effect sizes, while error bars are the 95% confidence intervals. Grey bands have been added to aid visualization.\u003c/p\u003e","description":"","filename":"floatimage4.png","url":"https://assets-eu.researchsquare.com/files/rs-8889532/v1/b4809fae01fa5f80ad7dede2.png"},{"id":104401647,"identity":"cfdb6f20-8f4c-4bcb-8a56-7a8b989a0abc","added_by":"auto","created_at":"2026-03-11 12:13:12","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":105616,"visible":true,"origin":"","legend":"\u003cp\u003eBoxplots comparing aquatic macroinvertebrate counts (top) and weight in grams (bottom) in control (orange) and treatment (dark green) impoundments before (left) and after (right) treatment. Each data point represents pooled data from five sweeps per impoundment per year. Unfilled circles indicate outliers and filled circles represent the raw data. All data are from macroinvertebrate sweeps in impoundments in southeastern New Brunswick collected 2021 – 2023.\u003c/p\u003e","description":"","filename":"floatimage5.png","url":"https://assets-eu.researchsquare.com/files/rs-8889532/v1/b0e6a83aea318d6b628aba9c.png"},{"id":104410512,"identity":"1f001446-685f-425f-8da2-d1cb4d3b4e55","added_by":"auto","created_at":"2026-03-11 12:52:28","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3069367,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-8889532/v1/485522a4-c311-4285-83f1-72458aa71351.pdf"},{"id":103931939,"identity":"1ceace55-c002-4b63-a4be-3146b1d212c3","added_by":"auto","created_at":"2026-03-04 16:41:28","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":48487,"visible":true,"origin":"","legend":"","description":"","filename":"Appendix.docx","url":"https://assets-eu.researchsquare.com/files/rs-8889532/v1/3a545fdd085f97904b81703d.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"Water level manipulations in human-made impoundments drive species- and guild-specific responses in wetland bird communities","fulltext":[{"header":"Introduction","content":"\u003cp\u003eWetlands, the transition zones between terrestrial and aquatic environments, provide critical ecosystem services and support rich biodiversity. These services include carbon sequestration, flood mitigation, water storage, and habitat for diverse wildlife (Mitsch and Gosselink \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2007\u003c/span\u003e, Mitsch et al. \u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e2015\u003c/span\u003e). Despite their importance, over 50% of the world\u0026rsquo;s natural wetlands have been lost since the 1700s (Davidson \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2014\u003c/span\u003e, Fluet-Chouinard et al. \u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e2023\u003c/span\u003e), with particularly severe losses in coastal regions where human settlement has historically concentrated (Mitsch and Gosselink \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e2007\u003c/span\u003e, Barbier et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2011\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eHuman-made wetlands, such as impoundments, are commonly constructed to offset wetland loss and compensate for some of the ecosystem services provided by natural wetlands, particularly habitat for waterfowl and other wetland wildlife (Keith \u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e1961\u003c/span\u003e). Although impoundments can provide important wildlife habitat, managers have long observed declines in nutrient availability, changes in invertebrate communities, and reduced wildlife use as impoundments age (Kadlec \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1962\u003c/span\u003e, Baldassarre and Bolen \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2006\u003c/span\u003e, Demers \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2021\u003c/span\u003e, Rawal et al. \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e2026\u003c/span\u003e). This process, known as wetland senescence, occurs as static, human-controlled water levels promote vegetation succession and limit nutrient cycling, leading to reduced habitat quality and productivity over time (Fredrickson \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e1985\u003c/span\u003e, Loder et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2018a\u003c/span\u003e, \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003eb\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eWater-level drawdowns have been used since the mid-20th century as a management strategy to counteract wetland senescence and rejuvenate productivity in aging impoundments (Kadlec \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1962\u003c/span\u003e, Meeks \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1969\u003c/span\u003e). Drawdowns temporarily expose wetland sediments to aerobic conditions, stimulate decomposition of accumulated organic matter, and reset plant communities, thereby increasing nutrient availability upon reflooding (Baldassarre and Bolen \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). In many regions of North America, drawdowns have been associated with increased nutrient availability, macroinvertebrate production, and waterbird abundance, as well as shifts toward earlier successional vegetation communities (Kadlec \u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e1962\u003c/span\u003e, Meeks \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e1969\u003c/span\u003e, Lumsden et al. \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, Schummer et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eImpoundments support a wide range of wetland wildlife, and drawdowns can create dynamic habitat conditions that benefit different groups of birds at different stages of water-level manipulation (Rundle and Fredrickson 1981, Kaminski et al. \u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e2006\u003c/span\u003e). Shallow water and exposed mudflats during drawdown can provide foraging habitat for shorebirds and dabbling waterfowl, whereas refilled impoundments may favor diving species that require deeper water (Taft et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Although drawdowns are often implemented to improve habitat conditions for waterfowl, they may also influence non-target species and overall bird community composition, highlighting the importance of evaluating both community-level and species-specific responses.\u003c/p\u003e \u003cp\u003eIn Atlantic Canada, coastal wetlands are particularly important for breeding, migrating, and overwintering birds along the Atlantic Flyway (Erwin \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1996\u003c/span\u003e), yet these systems have experienced extensive historical loss. In the Maritime provinces, at least two-thirds of coastal wetlands were lost following European settlement as wetlands were dyked and drained for agriculture and development (Government of Canada \u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e1991\u003c/span\u003e, Butzer \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). To compensate for these losses, Ducks Unlimited Canada and the Canadian Wildlife Service constructed numerous impoundments beginning in the mid-20th century (Loder et al. \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2019\u003c/span\u003e), often on former coastal wetlands underlain by marine-derived clays and silts (van Proosdij et al. \u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e2010\u003c/span\u003e, Loder et al. \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e2018a\u003c/span\u003e). These impoundments differ from those in other regions of North America because they occur on nutrient-poor, marine-derived soils, and evidence of wetland senescence has been documented through declining nutrients, altered macroinvertebrate communities, and reduced wildlife use (Loder et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2018b\u003c/span\u003e, Demers \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eDespite widespread use of drawdowns elsewhere, there is little peer-reviewed research evaluating drawdown effects in coastal impoundments of Atlantic Canada, where ecological responses may differ from those observed in freshwater inland systems. Loder et al. (\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e2019\u003c/span\u003e) found that freshwater impoundments built on marine-derived soils in the Nova Scotia \u0026ndash; New Brunswick border region had generally higher nutrients than freshwater waterbodies managed for waterfowl in other areas of North America but were less productive than shallow wetlands in the Prairie Pothole Region. Moreover, most drawdown studies have focused on overwintering habitats in southern regions (e.g., Wiebe \u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e1946\u003c/span\u003e, Taft et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2002\u003c/span\u003e), leaving uncertainty about drawdown effects on breeding and migratory bird communities in northern coastal systems. Here, we used a Before-After-Control-Impact (BACI) design to evaluate the effects of water-level drawdowns on bird communities, focal species, and aquatic macroinvertebrates in coastal impoundments of southeastern New Brunswick. By integrating community-level, species-level, and mechanistic responses, we aimed to assess whether drawdowns function as an effective management tool in this region and to identify potential trade-offs among taxa.\u003c/p\u003e \u003cp\u003eWe hypothesized that water-level drawdowns alter bird use of impoundments by changing habitat structure and food availability. We predicted increased macroinvertebrate abundance and biomass following reflooding, leading to higher bird occupancy and abundance at post-treatment wetlands relative to pre-treatment conditions and control sites. We further predicted that responses would vary among species and foraging groups, with shallow-water foragers responding positively during drawdown and aquatic diving species responding negatively due to reduced water depth.\u003c/p\u003e"},{"header":"Methods","content":"\u003ch4\u003eStudy locations\u003c/h4\u003e\n\u003cp\u003eWe monitored freshwater impoundments in southeastern New Brunswick, Canada (45.910, -64.306). Seven impoundments were selected for experimental drawdown treatment, each paired with at least one nearby unmanipulated impoundment serving as a control. Additional control sites occurred in clusters where no impoundments were selected for manipulation. In total, we monitored 19 impoundments (control: \u003cem\u003en\u003c/em\u003e = 12; treatment: \u003cem\u003en\u003c/em\u003e = 7; Figure 1; Appendix 1). Impoundments were selected based on accessibility, proximity to other impoundments, and recommendations from Ducks Unlimited Canada biologists and collaborating researchers. Assignment of treatment and control status occurred after collection of baseline data on birds, macroinvertebrates, and vegetation, and incorporated logistical constraints. All drawdowns were administered by Ducks Unlimited Canada.\u003c/p\u003e\n\u003cp\u003eAll impoundments were freshwater systems constructed on former coastal dykelands and occurred in pairs or clusters (Figure 1; Appendix 1). Each was bounded by an earthen berm with a water control structure allowing manipulation of water levels (Kelly et al. 1993). Surrounding land use included agriculture, forest, National Wildlife Areas, and rural properties. Impoundments were located near the Bay of Fundy, the Memramcook River, channelized ditches, or bogs, and were managed by Ducks Unlimited Canada or the Canadian Wildlife Service.\u003c/p\u003e\n\u003cp\u003eWe surveyed all impoundments at least once per week during three field seasons (early April - late September 2021\u0026ndash;2023), spanning the breeding season and portions of spring and fall migration. In 2021, we collected pre-treatment data on wetland bird occupancy and abundance and macroinvertebrate abundance and biomass. Occupancy was defined as presence/non-detection, and abundance as counts of individuals per wetland. Macroinvertebrate biomass was measured as total dry mass per wetland per year.\u003c/p\u003e\n\u003cp\u003eWater control structures (e.g., stop logs) were removed in late winter 2022, and wetlands were allowed to drain through the summer drawdown period (Figure 2). Structures were reinstalled in fall 2022, and impoundments refilled passively via precipitation and snowmelt over winter. Post-treatment data were collected in 2023. During drawdowns, water remained in borrow pits along impoundment margins. One treatment wetland failed to drain and refill fully and was excluded from analyses. All remaining treatment wetlands refilled to normal operating levels prior to 2023 surveys, therefore, we collected three years of monitoring at 19 wetlands: 2021 was monitored as pre-treatment, 2022 was monitored as 7 treatment and 12 controls, and 2023 was monitored as 7 post-treatment and 12 controls (with one treatment removed during analyses).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eWetland bird surveys\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eBird surveys were conducted by one or two observers walking the perimeter of each impoundment and recording all birds seen or heard within wetland boundaries. Songbirds were recorded as presence/non-detection only, as they were not the focus of this study. Presence/non-detection of mammals, amphibians, and reptiles was also noted. Survey duration varied with wetland size and typically ranged from 30\u0026ndash;75 minutes. At two sites, perimeter surveys were not feasible due to dense vegetation or closely adjacent impoundments. These sites were surveyed using spotting scopes from fixed vantage points. Survey methods were consistent within each wetland across years. Surveys began when light conditions allowed accurate visual identification of waterfowl (i.e., just before sunrise on clear days). Surveys were not initiated more than five hours after sunrise and were not conducted during rain or heavy fog.\u003c/p\u003e\n\u003cp\u003eFor adjacent impoundments separated by a center dyke, both observers walked the dyke simultaneously to reduce double-counting. For adjacent sites without a center dyke, observers coordinated via handheld radios to confirm bird movements between wetlands. Birds entering the wetland during surveys were counted only if observers were confident movements were unrelated to observer disturbance. Flyovers were excluded unless birds were actively interacting with the wetland (e.g., foraging swallows, hunting raptors). Flyovers were rare and unlikely to influence counts.\u003c/p\u003e\n\u003cp\u003eAt the start of each survey, observers recorded date, time, weather conditions (precipitation, wind, temperature), and disturbance (i.e., anything that might influence detection such as highway noise or passing trains). A standardized photograph was taken from the survey starting point to document seasonal vegetation change.\u003c/p\u003e\n\u003ch4\u003eMacroinvertebrate sampling\u003c/h4\u003e\n\u003cp\u003eMacroinvertebrates were sampled in late May of each year, coinciding with peak waterfowl nesting and brood-rearing periods (Schummer et al. 2021). Sampling followed methods outlined by Demers (2021) using a D-frame dip net. At each wetland, five randomly selected shoreline points were sampled annually using a standardized two-meter V-shaped sweep with three bottom-contact bounces. Samples were rinsed into sealable plastic bags using impoundment water. Macroinvertebrates \u0026gt;4 mm were sorted from debris and vegetation, identified to Order, counted, and preserved in ethanol. Abundance was calculated by pooling counts across all five samples into a single wetland-level estimate per year.\u003c/p\u003e\n\u003cp\u003eIn 2024, preserved samples were transferred to coffee filters, drained, and air-dried. Filters containing invertebrates were weighed to estimate biomass. Mean filter mass (1.96 g), calculated from three unused filters, was subtracted from all sample weights to estimate total macroinvertebrate biomass (g dry mass) per wetland per year.\u003c/p\u003e\n\u003ch4\u003eAdditional site-level data\u003c/h4\u003e\n\u003cp\u003eWe derived site-level vegetation metrics using Sentinel-2 Level-2A imagery accessed through the Copernicus Data Space Ecosystem Browser (Copernicus Data Space Ecosystem 2024). We calculated mean Normalized Difference Vegetation Index (NDVI; Pettorelli et al. 2005) for each site by month during the survey period.\u003c/p\u003e\n\u003cp\u003eTo reduce inter-site variation unrelated to treatment, we calculated relative NDVI by subtracting each site\u0026rsquo;s mean seasonal NDVI from monthly NDVI values. This standardized NDVI values relative to each site\u0026rsquo;s baseline greenness, where positive monthly values are greater and negative values are lesser that average greenness per site. Wetland area (km\u0026sup2;) was extracted from the same imagery source.\u003c/p\u003e\n\u003ch3\u003e\u003cstrong\u003eStatistical analyses\u003c/strong\u003e\u003c/h3\u003e\n\u003ch4\u003e\u003cstrong\u003eGeneralized additive models\u003c/strong\u003e\u003c/h4\u003e\n\u003cp\u003eWe used generalized additive mixed models (GAMMs) to test treatment effects and to examine temporal patterns in bird use of impoundments. Models were fit using the \u003cstrong\u003emgcv\u003c/strong\u003e package in R (v1.9-3; Wood 2017). We used cubic regression splines (basis = \u003ccode\u003e\u0026quot;cr\u0026quot;\u003c/code\u003e) with a fixed basis dimension of \u003cem\u003ek\u003c/em\u003e\u003cstrong\u003e\u0026nbsp;\u003c/strong\u003e= 4 to enhance interpretability and reduce overfitting. Seasonal patterns were modeled using a smooth term for ordinal date. To account for repeated surveys at the same wetlands, site was included as a random effect using a random-effect smooth (\u003ccode\u003ebs = \u0026quot;re\u0026quot;\u003c/code\u003e).\u003c/p\u003e\n\u003cp\u003eAbundance models were fit using a negative binomial error distribution, while occupancy models used a binomial distribution with a logit link. The \u003cstrong\u003etrplus\u003c/strong\u003e package (v1.2-4; Delignette-Muller and Dutang 2015) was used to guide selection of appropriate error distributions. Model selection was based on Akaike\u0026rsquo;s Information Criterion (AIC), beginning with a global model and sequentially removing terms; models within \u0026Delta;AIC \u0026lt; 2 were considered competitive. Estimated degrees of freedom (edf) were examined to distinguish linear (edf \u0026asymp; 1) from non-linear effects. We used a threshold of \u0026alpha; = 0.05 for significance but report marginal significance at \u0026alpha; = 0.10 to show general patterns.\u003c/p\u003e\n\u003cp\u003eGlobal models for each species or species group included ordinal date, wetland area (km\u0026sup2;), aquatic macroinvertebrate biomass (g), year, and treatment, with site included as a random effect. Treatment was included as both a main effect and, where supported by the data, as an interaction with ordinal date. For species with low sample sizes (e.g., Pied-billed Grebe \u003cem\u003ePodilymbus podiceps\u003c/em\u003e and Sora \u003cem\u003ePorzana carolina\u003c/em\u003e), the treatment \u0026times; date interaction was not estimable and was removed. Because detection probability declined later in the season, most analyses used early-season data (April\u0026ndash;June). Relative NDVI was excluded due to strong collinearity with ordinal date (r \u0026gt; 0.7) and low seasonal variability during this period.\u003c/p\u003e\n\u003ch4\u003e\u003cstrong\u003eCommunity-level response variables\u003c/strong\u003e\u003c/h4\u003e\n\u003cp\u003eWe assessed community-level bird responses using survey count data for all waterbird species. Songbirds were excluded because only presence/non-detection data were collected. In addition to analyzing the full bird community, we grouped species into three foraging guilds, Aquatic Surface Herbivores, Aquatic Diving Predators, and Aquatic Ground Predators, based on Avibase classifications (Lepage 2024; Appendix 2). These guilds represent ecologically meaningful groups and allowed inclusion of species with insufficient detections for species-level modeling.\u003c/p\u003e\n\u003cp\u003eFor swallows (four locally occurring species), we modeled occupancy using the full April\u0026ndash;September dataset because detection remained high throughout the season due to their aerial foraging behavior. Swallows are aerial insectivores, a guild of conservation concern across North America (Birds Canada and Environment and Climate Change Canada 2024).\u003c/p\u003e\n\u003ch4\u003e\u003cstrong\u003eBACI analyses for community and macroinvertebrate responses\u003c/strong\u003e\u003c/h4\u003e\n\u003cp\u003eTo explicitly test for Before\u0026ndash;After\u0026ndash;Control\u0026ndash;Impact (BACI) effects, we conducted additional analyses examining whether changes through time differed between Treatment and Control wetlands (Chevalier et al. 2019).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSite-level BACI\u0026nbsp;\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;We calculated site-level mean values for each response variable (total bird abundance, macroinvertebrate abundance, and macroinvertebrate biomass) for each period (Before = 2021; After = 2023). For each site, we computed the change through time (\u0026Delta; = After \u0026minus; Before) and compared \u0026Delta; values between Treatment and Control sites using linear models.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMixed-effects BACI models\u003c/strong\u003e\u003cbr\u003e\u0026nbsp;To incorporate all survey-level data, we fit mixed-effects BACI models of the form response (occupancy or abundance) by treatment (control or impact) with an interaction with period (before or after), where the Treatment \u0026times; Period interaction represents the BACI framework. Site was included as a random effect to account for repeated measurements. For bird abundance, we additionally fit GAMMs including a Treatment \u0026times; Period interaction and a smooth term for ordinal date to account for seasonal dynamics.\u003c/p\u003e\n\u003ch4\u003e\u003cstrong\u003eSpecies-level response variables\u003c/strong\u003e\u003c/h4\u003e\n\u003cp\u003eWe modeled occupancy for focal species detected in \u0026ge;20% of surveys (13 species; Appendix 2), representing the core wetland bird community in the study area (Birds Canada and Environment and Climate Change Canada 2024). All species-level analyses used early-season data only (April\u0026ndash;June) due to changes in detection probabilities after June.\u003c/p\u003e\n\u003ch4\u003e\u003cstrong\u003eMacroinvertebrate data analysis\u003c/strong\u003e\u003c/h4\u003e\n\u003cp\u003eTo evaluate the effects of drawdowns on aquatic macroinvertebrates, we conducted both two-way factorial and one-way ANOVAs, depending on the comparison of interest. To align with the BACI design, we first used two-way ANOVAs with Treatment (Control vs. Impact) and Time (Before vs. After) as fixed factors, including the Treatment \u0026times; Time interaction. Tukey HSD tests were used for post-hoc comparisons when main effects were significant (\u0026alpha; = 0.05).\u003c/p\u003e\n\u003cp\u003eSecond, to compare macroinvertebrate responses among management categories (Untreated, Drawdown, Post-treatment), we conducted one-way ANOVAs for abundance and biomass, followed by Tukey HSD tests. Because our primary ecological interest was in whether drawdowns produced lasting effects, interpretation focused on comparisons between Untreated and Post-treatment wetlands.\u003c/p\u003e\n\u003cp\u003eAll analyses were conducted in R v4.4.1 (R Core Team 2024).\u003c/p\u003e"},{"header":"Results","content":"\u003ch2\u003e\u003cem\u003eCommunity-level response\u003c/em\u003e\u003c/h2\u003e\n\u003cp\u003eDuring 1,529 surveys conducted from April\u0026ndash;September 2021\u0026ndash;2023, we recorded 108 avian species using our focal impoundments. Analyses focused on birds for which abundance data were collected. Overall bird abundance did not respond strongly to the drawdown phase, although a potential weak negative effect was detected (\u0026beta; = -0.18, 95% CI = -0.14 to 0.59, p = 0.09). In contrast, overall bird abundance showed a significant positive response to the post-treatment stage, with higher abundance at post-treatment sites relative to untreated sites following reflooding (\u0026beta; = 0.37, 95% CI =\u0026nbsp;-0.03 to 0.17,\u0026nbsp;p \u0026lt; 0.001).\u003c/p\u003e\n\u003cp\u003eFor foraging guilds, Aquatic Ground Predators responded positively during the drawdown phase, whereas Aquatic Diving Predators showed significant negative responses during both the drawdown and post-treatment stages (Figure 4; Appendix 3). Aquatic Surface Herbivores exhibited reduced abundance during drawdown but increased abundance following refilling of the impoundments. Swallow occupancy was positively associated with the post-treatment stage, with higher site occupancy after refilling compared to untreated sites (Figure 3; Appendix 3).\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eSite-level BACI analyses indicated greater increases in total bird abundance at Impact wetlands than at Control wetlands between the Before and After periods; however, responses varied substantially among sites. The estimated treatment effect was positive but marginal (\u0026beta; = 44.0, 95% CI = -5.69 to 93.8, p = 0.08), reflecting possible increases at a subset of Impact wetlands and little change at others.\u003c/p\u003e\n\u003cp\u003eIn contrast, mixed-effects BACI models incorporating all survey-level data revealed a strong positive treatment effect. The Treatment \u0026times; Period interaction was significant, indicating that bird abundance increased at Impact wetlands relative to Controls following drawdown (\u0026beta; = 27.1, 95% CI = 13.9 to 40.3). There was no evidence of pre-treatment differences between Impact and Control wetlands, and Control sites showed little temporal change.\u003c/p\u003e\n\u003ch2\u003e\u003cem\u003eSpecies-level response\u003c/em\u003e\u003c/h2\u003e\n\u003cp\u003eWe examined species-level occupancy responses for nine waterfowl species, two waterbird species, and two songbird species (Appendix 4). During the drawdown phase, Blue-winged Teal (\u003cem\u003eSpatula discors\u003c/em\u003e) and Green-winged Teal (\u003cem\u003eAnas carolinensis\u003c/em\u003e) showed significant positive occupancy responses, whereas Ring-necked Duck (\u003cem\u003eAythya collaris\u003c/em\u003e), Wood Duck (\u003cem\u003eAix sponsa\u003c/em\u003e), Pied-billed Grebe, and Sora showed significant negative responses (Figure 4; Appendix 4).\u003c/p\u003e\n\u003cp\u003eNo species exhibited strong positive responses during the post-treatment stage. Ring-necked Duck and Pied-billed Grebe showed reduced occupancy following impoundment refilling relative to untreated sites. Swamp Sparrow (\u003cem\u003eMelospiza georgiana\u003c/em\u003e) showed a weak positive post-treatment response, consistent with patterns observed for the Swallow group, although parameter estimates were small (Figure 4; Appendices 2 and 3).\u003c/p\u003e\n\u003ch2\u003e\u003cem\u003eMacroinvertebrate response\u003c/em\u003e\u003c/h2\u003e\n\u003cp\u003eSite-level and mixed-effects BACI analyses indicated contrasting macroinvertebrate responses between Control and Treatment wetlands (Figure 5). Macroinvertebrate abundance increased at Control wetlands between 2021 and 2023, whereas Treatment wetlands exhibited a significantly smaller change through time (BACI difference = -112.2, 95% CI = -195.0 to -29.1, p = 0.01). Dry biomass showed a similar but weaker pattern, with reduced or delayed increases at Treatment wetlands relative to Controls (BACI difference = -0.218 , 95% CI = -0.459 to 0.022, p = 0.07). \u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eWe found that overall bird abundance tended to increase in coastal impoundments following drawdown treatment, although responses varied among taxa, foraging groups, and individual wetlands. These results indicate that water-level manipulation can influence a broader suite of wildlife than the waterfowl typically targeted by impoundment management, including species of conservation concern. As such, conservation managers must consider not only target species but also the wider ecological consequences of water-level manipulation.\u003c/p\u003e \u003cdiv id=\"Sec20\" class=\"Section2\"\u003e \u003ch2\u003eCommunity-level responses\u003c/h2\u003e \u003cp\u003eWe found support for the hypothesis that drawdowns increase bird abundance in the post-treatment phase, with a significant positive response detected when repeated surveys and site-level variation were accounted for. Although site-level BACI analyses indicated substantial heterogeneity among wetlands and were marginally non-significant, both GAMM analyses and mixed-effects BACI models consistently indicated increased bird use of drawdown wetlands following reflooding. Together, these results suggest that drawdowns can increase overall wetland bird abundance under favorable conditions, consistent with findings from other regions of North America where drawdowns are commonly used to rejuvenate impoundments (Suring and Knighton \u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e1985\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eResponses among foraging guilds differed markedly during the drawdown phase. Aquatic Ground Predators responded positively, whereas Aquatic Surface Herbivores and Aquatic Diving Predators showed negative responses. These patterns are consistent with differences in habitat requirements among groups. Diving species typically forage in deeper water (\u0026gt;\u0026thinsp;25 cm; Taft et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2002\u003c/span\u003e, Baschuk et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), whereas dabbling ducks prefer shallow water habitats (5\u0026ndash;25 cm; Isola et al. \u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e2000\u003c/span\u003e, Taft et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Shorebirds, which comprise a large proportion of the Aquatic Ground Predator group, preferentially forage in shallow water and exposed substrates created during drawdowns (Rundle and Fredrickson 1981).\u003c/p\u003e \u003cp\u003eBird abundance at post-treatment sites peaked in late April to mid-May, coinciding with peak shorebird migration through this portion of the Atlantic Flyway (Erwin \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e1996\u003c/span\u003e, eBird \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2024\u003c/span\u003e). If drawdowns are incorporated into future management plans, timing drawdowns to coincide with shorebird migration could enhance the value of these impoundments as stopover habitat. Migratory shorebird populations have declined by approximately 42% in Canada since 1980, with wetland and coastal habitat loss considered a major contributing factor (Birds Canada and Environment and Climate Change Canada 2024). Consequently, management actions that alter habitat availability during migration periods warrant careful consideration.\u003c/p\u003e \u003cp\u003eDuring the post-treatment phase, Aquatic Diving Predators continued to show a negative response, although the magnitude was weaker than during drawdown. In contrast, Aquatic Surface Herbivores exhibited a positive post-treatment response, with increased abundance of dabbling ducks, particularly American Black Duck (\u003cem\u003eAnas rubripes\u003c/em\u003e) and Mallard (\u003cem\u003eA. platyrhynchos\u003c/em\u003e), following refilling. We did not detect corresponding changes in occupancy for these two species, suggesting that drawdowns influenced the intensity of site use rather than site selection. This distinction highlights the importance of considering both occupancy and abundance metrics when evaluating habitat management outcomes.\u003c/p\u003e \u003cp\u003eOccupancy by swallows increased during the post-treatment phase, indicating that refilled impoundments may provide improved habitat for aerial insectivores. Most drawdown research has focused on waterfowl, yet wetlands support a wide range of taxa for foraging, nesting, and migration (Griffin \u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e1982\u003c/span\u003e, Cooper and Campbell \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e1997\u003c/span\u003e). To our knowledge, this is the first examination of drawdown effects on aerial insectivores. Previous work in the Chignecto Isthmus identified impoundments as important swallow roosting habitat (Saldanha \u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e2016\u003c/span\u003e, Fensore \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), and the positive post-treatment response observed here may reflect increased availability of emergent insects following reflooding. Because macroinvertebrate sampling only occurred once per season and may have missed short-lived emergence pulses, future research should explicitly examine emergent insect dynamics and aerial prey availability following drawdowns.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec21\" class=\"Section2\"\u003e \u003ch2\u003eSpecies-level responses\u003c/h2\u003e \u003cp\u003eSpecies-level responses were variable but generally consistent with community-level patterns. Species-level results were interpreted cautiously and were primarily used to identify directional responses consistent with broader community-level trends, rather than to infer precise species-specific effect sizes. Several species, including Pied-billed Grebe, Sora, Ring-necked Duck, and Wood Duck, responded negatively during the drawdown phase. This was likely due to reduced water depth or overall wetland area. Wood Duck, for example, have been reported to forage at depths of 19\u0026ndash;40 cm (Drobney and Fredrickson 1979) and reduced water levels may limit suitable foraging habitat. Sora densities have been reported to be similar between drawdown and high-water sites elsewhere (Baschuk et al. \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e2012\u003c/span\u003e), suggesting that factors beyond food availability, such as vegetation structure or habitat configuration, may influence their response to drawdown.\u003c/p\u003e \u003cp\u003eIn contrast, Green-winged Teal and Blue-winged Teal showed positive occupancy responses during drawdown, consistent with their reliance on shallow water and mudflat habitats (Bellrose \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e1980\u003c/span\u003e). Although no species exhibited strong positive occupancy responses during the post-treatment phase, exploratory analyses indicated increased abundance of American Black Duck, Mallard, and Green-winged Teal following refilling.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec22\" class=\"Section2\"\u003e \u003ch2\u003eMacroinvertebrate responses\u003c/h2\u003e \u003cp\u003eWe did not find support for the hypothesis that drawdowns increased aquatic macroinvertebrate abundance or biomass within one year of refilling. Instead, both metrics were lower at treatment wetlands relative to controls, despite increased bird abundance. Similar outcomes have been reported elsewhere, where water-level manipulation reduced macroinvertebrate abundance following refilling (McEwen and Butler 2009), although other studies have documented increased macroinvertebrate abundance or biomass in wetlands following water-level changes (Anderson and Smith 2000, Schummer et al. \u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003cp\u003eA drawdown study conducted near our project area reported increased nutrient availability following drawdown but, similar to our own results, the study found lower macroinvertebrate abundance and biomass in treatment wetlands compared to controls (Hanson \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e1993\u003c/span\u003e), suggesting that recovery of macroinvertebrate communities may lag behind nutrient responses. Although some treatment sites in our study exhibited higher macroinvertebrate counts or biomass, most showed negative responses. Because macroinvertebrates were sampled once per season in late May, it is possible that recovery occurred later in the season or that pulses in abundance were missed due to a single sampling period per season. However, previous work in local wetlands found limited seasonal variation in macroinvertebrate abundance and biomass (Pollet et al. \u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e2026\u003c/span\u003e), suggesting that timing alone is unlikely to fully explain observed patterns.\u003c/p\u003e \u003cdiv id=\"Sec23\" class=\"Section3\"\u003e \u003ch2\u003eRecommendations\u003c/h2\u003e \u003cp\u003eResponses by bird and macroinvertebrate communities to water-level drawdowns were mixed, highlighting the importance of aligning management actions with clearly defined conservation objectives. In Atlantic Canada, wildlife managers should consider which species or functional groups are being targeted before implementing drawdowns, as this management action benefitted some taxa (e.g., Green-winged Teal, Blue-winged Teal, swallows, Aquatic Surface Herbivores, and Aquatic Ground Predators) while negatively affecting others (e.g., Ring-necked Duck, Pied-billed Grebe, Sora, Wood Duck, and Aquatic Diving Predators). In addition, some groups responded positively only during the drawdown phase and not after refilling, indicating that benefits may be temporally limited and that timing is crucial.\u003c/p\u003e \u003cp\u003eGiven these trade-offs, we recommend managing impoundments on a rotating drawdown schedule, whereby some wetlands remain at normal operating levels while others undergo drawdown. This approach would allow managers to provide a mosaic of habitat conditions that support a broader range of wetland birds, including species with differing water-depth requirements (Rundle and Fredrickson 1981, Taft et al. \u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e2002\u003c/span\u003e). Because impoundments in Atlantic Canada frequently occur in clusters, manipulating only one impoundment per cluster at a time may be particularly effective for increasing habitat heterogeneity at the landscape scale. Habitat heterogeneity is a well-established driver of biodiversity (MacArthur and MacArthur \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e1961\u003c/span\u003e), particularly at the landscape scale in heavily-modified habitats or agroecosystems (Fahrig et al. \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2015\u003c/span\u003e, Wilson et al. \u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e2017\u003c/span\u003e, de Zwaan et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2022\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e2024\u003c/span\u003e), and may help balance competing habitat needs among wetland bird communities.\u003c/p\u003e \u003cp\u003eAlthough this study focused on short-term responses to a single year of drawdown and refilling, longer-term monitoring would improve understanding of how drawdowns influence wetland productivity and wildlife use over time. Continued monitoring of impoundments post-drawdown would be particularly valuable for evaluating delayed or cumulative responses in macroinvertebrate communities and bird use during the early breeding and migration period (April\u0026ndash;June). Longer-term data would also help clarify how drawdowns interact with processes of wetland senescence, which previous research suggests may recur within five to seven years after impoundment construction in this region (Loder et al. \u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e2018b\u003c/span\u003e, Demers \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2021\u003c/span\u003e).\u003c/p\u003e \u003c/div\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eWater-level manipulation has long been used as a tool to improve habitat conditions in managed impoundments, yet its ecological consequences extend beyond waterfowl to a diverse array of wetland wildlife. Our results demonstrate that drawdowns can increase overall bird abundance in coastal impoundments of Atlantic Canada, while simultaneously generating trade-offs among species and functional groups. These findings highlight that drawdowns are not a universally beneficial management action, but rather one that reshapes habitat availability in ways that benefit some taxa while negatively influencing others.\u003c/p\u003e \u003cp\u003eRecognizing and managing these trade-offs is critical for effective wetland stewardship. Strategies that promote spatial and temporal heterogeneity, such as rotating drawdowns among clustered impoundments, may allow managers to maximize biodiversity and support a wider range of wetland birds through time and space. By integrating community-level responses, species-level patterns, and mechanistic insights from macroinvertebrate dynamics, this study provides a regionally relevant framework for evaluating and refining drawdown-based management in coastal impoundments of Atlantic Canada.\u003c/p\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFunding and support for this project was provided by a Mitacs Accelerate award to K. Owen (IT20776), Ducks Unlimited Canada, New Brunswick Wildlife Trust Fund, Nova Scotia Habitat Conservation Fund (contributions from hunters and trappers), Acadia University, University of New Brunswick, and Wildlife Habitat Canada. We thank field technicians Hannah Drake, Sarah Neima, Emily Peacock, Ruby Schweighardt, Fawn Maika, and Joel Eckerson, as well as several volunteers. We thank Al Hanson, Graham Forbes, Laura Tranquilla, and Tom Beckley for comments throughout the project, and Myriam Barbeau, Chris Edge, Wendy Monk, and Kate Sherren for additional comments on a final draft. Finally, we thank reviewers for their insights that helped improve our manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eFunding\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by funding from\u0026nbsp;a Mitacs Accelerate award to K. Owen (IT20776), Ducks Unlimited Canada, New Brunswick Wildlife Trust Fund, Nova Scotia Habitat Conservation Fund (contributions from hunters and trappers), Acadia University, University of New Brunswick, and Wildlife Habitat Canada.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eCompeting Interests\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe authors have no relevant financial or non-financial interests to disclose.\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eAuthor Contributions\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eAll authors contributed to study conception and design. Kiirsti Owen completed data collection, analysis, and wrote the manuscript. All authors provided comments on the manuscript and approved the final version\u003c/p\u003e\n\u003cp\u003e\u003cem\u003e\u003cstrong\u003eData Availability\u003c/strong\u003e\u003c/em\u003e\u003c/p\u003e\n\u003cp\u003eThe datasets generated during this study are available from the corresponding author on reasonable request.\u003cbr\u003e\u0026nbsp;\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBaldassarre GA, Bolen EG (2006) Waterfowl Ecology and Management. 2\u003csup\u003end\u003c/sup\u003e Edition. John Wiley \u0026amp; Sons. New York, NY, USA\u003c/li\u003e\n\u003cli\u003eBarbier EB, Hacker SD, Kennedy C, Koch EW, Stier AC, Silliman BR (2011) The value of estuarine and coastal ecosystem services. 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Ecol Indic 83:218\u0026ndash;226. https://doi.org/10.1016/j.ecolind.2017.07.059\u003c/li\u003e\n\u003cli\u003eWood S (2017) \u003cem\u003eGeneralized Additive Models: An Introduction with R\u003c/em\u003e, 2\u003csup\u003end\u003c/sup\u003e edition. Chapman and Hall/CRC.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"wetlands-ecology-and-management","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wetl","sideBox":"Learn more about [Wetlands Ecology and Management](https://www.springer.com/journal/11273)","snPcode":"11273","submissionUrl":"https://submission.nature.com/new-submission/11273/3","title":"Wetlands Ecology and Management","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"aquatic macroinvertebrates, coastal impoundments, drawdown, habitat management, waterfowl, wetland senescence","lastPublishedDoi":"10.21203/rs.3.rs-8889532/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-8889532/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFor over half a century, wildlife managers have constructed impoundments to offset wetland habitat loss across North America. As impoundments age, productivity often declines, and water-level drawdowns are commonly used to rejuvenate habitat and primary productivity and increase wildlife use, particularly targeting wetland bird communities. We evaluated the effectiveness of drawdowns in coastal impoundments of Atlantic Canada, where responses to management are poorly understood. From April\u0026ndash;June 2021\u0026ndash;2023, we used a replicated before\u0026ndash;after\u0026ndash;control\u0026ndash;impact (BACI) design to assess bird occupancy and abundance at untreated, drawdown, and post-treatment wetlands using generalized additive and mixed-effects models. We also tested the response of aquatic macroinvertebrates to drawdown. Bird responses varied among foraging guilds and species. Shallow-water foragers, including aquatic ground predators and some dabbling ducks, increased during drawdown, whereas aquatic diving species declined. Following refilling, overall bird abundance increased significantly at treatment wetlands relative to controls. Aquatic macroinvertebrate abundance did not increase after drawdown, suggesting that bird responses were more strongly linked to changes other than standing prey biomass. These findings indicate that drawdowns can enhance wetland bird use but generate trade-offs among species with different functional traits and habitat requirements. Managing impoundments on a rotating drawdown schedule to maintain habitat heterogeneity at a landscape scale may help maximize biodiversity and support a broader range of wetland birds in Atlantic Canada.\u003c/p\u003e","manuscriptTitle":"Water level manipulations in human-made impoundments drive species- and guild-specific responses in wetland bird communities","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-04 16:41:23","doi":"10.21203/rs.3.rs-8889532/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-04-20T23:59:03+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-10T22:54:32+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-04-10T16:06:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"23025353832351502611400473436115648420","date":"2026-03-21T23:22:24+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-20T17:25:10+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"192757096044748200797466848496082280434","date":"2026-03-20T13:44:58+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"30469522685380932808172427878780794093","date":"2026-02-27T07:40:51+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-02-27T03:11:39+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-02-19T03:06:13+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-02-17T12:38:14+00:00","index":"","fulltext":""},{"type":"submitted","content":"Wetlands Ecology and Management","date":"2026-02-16T04:17:30+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"wetlands-ecology-and-management","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"wetl","sideBox":"Learn more about [Wetlands Ecology and Management](https://www.springer.com/journal/11273)","snPcode":"11273","submissionUrl":"https://submission.nature.com/new-submission/11273/3","title":"Wetlands Ecology and Management","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"2dc88de5-58f1-4c37-88e3-238f1e81221e","owner":[],"postedDate":"March 4th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[],"tags":[],"updatedAt":"2026-05-15T19:23:05+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-04 16:41:23","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-8889532","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-8889532","identity":"rs-8889532","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}