Abstract Long-term population monitoring at key nonbreeding sites is critical for assessing the conservation status of long-distance migratory shorebirds. We used a joint-likelihood Bayesian state-space model to estimate 26-year population trends (2000–2025) for Calidris canutus rufa (Red Knot) and Limosa haemastica (Hudsonian Godwit) at Bahía Lomas, Tierra del Fuego, Chile—the most important nonbreeding site for rufa Red Knots and one of the most important for L. haemastica. Aerial surveys transitioned from visual estimates (2000–2022) to photograph-based estimation analyzed post-survey (2020–2025), with paired counts in overlap years. The joint-likelihood specification allowed both observation methods to inform a single underlying population trajectory and provided a direct test for systematic differences between methods; the estimated method offset was indistinguishable from zero for both species. Calidris c. rufa declined by ∼63% between 2000 and 2025 (from ∼38,600 to ∼13,600 birds), with most of the decline occurring during 2000–2007 and the population stabilizing thereafter at ∼11,000–14,000 birds; the mean annual growth rate was –4.2% yr−1 (95% credible interval [95% CI]: –6.9% to –1.7%). Limosa haemastica showed no decisive directional trend across the same period (mean annual growth rate +1.5% yr−1, 95% CI: –1.4% to +3.7%) but high interannual variability. The contrasting trajectories—a clear long-term decline in C. c. rufa and substantial unstructured variability in L. haemastica—have distinct conservation implications: for C. c. rufa, maintaining a consistent local monitoring program at Bahía Lomas is instrumental for evaluating the long-term effectiveness of full-flyway management, whereas L. haemastica require a coordinated, regional monitoring framework spanning multiple South American nonbreeding sites to capture their unstructured variability.
Abstract Previous research on vertebrates suggests that numerous factors influence the initiation of seasonal movement behavior and potential reproductive carry-over effects. Recognizing the potential link between seasonal movements and reproductive carry-over effects, we investigated the drivers and potential consequences of spring movements consisting of movement transitions between the nonbreeding and breeding seasons in a large-bodied upland game bird, Meleagris gallopavo (Wild Turkey), using a spatial, morphometric, and disease data in Pennsylvania, USA. We fit 4 models to assess (1) environmental and individual drivers of seasonal movement, categorizing individuals that initiated seasonal movements as “movers” and individuals that did not exhibit seasonal movement as “residents”; (2) environmental and individual effects on movement-related energy expenditure (i.e., overall dynamic body acceleration); (3) effects of environmental variables, individual covariates, and movement-related energy on clutch size; and (4) effects of environmental variables, individual covariates, and movement-related energy on nest success. When modeling the influence of environmental and individual variables on spring movement initiation, we found that juveniles infected with lymphoproliferative disease virus were less likely to initiate a spring movement. When modeling the influence of environmental variables on movement-related energy during spring movements, we found that individuals expended greater movement-related energy in agricultural and developed areas. When modeling the influence of landscape variables encountered during spring movements on clutch size, we found that juvenile movers (n = 18) that encountered greater proportions of cropland and conifer forest laid more eggs than juvenile residents (n = 22). In addition, adult movers (n = 48) that encountered greater proportions of developed and higher primary road densities laid fewer eggs than adult residents (n = 130). Collectively, our findings suggest there are trade-offs with seasonal movement behavior in M. gallopavo, highlighting the broader ecological implications of alternative movement strategies and their linkages to reproductive carry-over effects.
Abstract Cacay (Caryodendron orinocense) is a native tree species increasingly cultivated in commercial plantations in the Colombian Orinoquía for its high-value nuts and oil, but the effects of this emerging tree crop on biodiversity remain poorly understood. We evaluated how cacay plantations influence bird taxonomic and functional diversity by comparing them with adjacent natural forests in the Colombian Orinoquía. Natural forests supported higher taxonomic and functional bird diversity than cacay plantations, where generalist bird species dominated and functional divergence and evenness were higher. Across both vegetation types, we recorded 117 bird species, including 3 Nearctic–Neotropical migrants detected primarily in natural forests. cacay plantations filtered out frugivores and nectarivores, contributing to ecological homogenization. Functional richness was higher in forests than in plantations, reflecting a broader functional space and the presence of species with extreme trait values, reinforcing the importance of natural forest for biodiversity conservation. RLQ ordination and fourth-corner analyses revealed that plantations were negatively associated with several sensitive guilds, including perch-foraging species, while favoring terrestrial and generalist bird species adapted to simplified landscapes. Landscape simplification reduced avian richness but maintained partially redundant functional assemblages in plantations. Although cacay plantations were dominated by generalist species occupying the remaining functional space, their functional resilience was constrained by the loss of key species and associated ecological functions. These findings underscore the importance of conserving remnant forests and promoting structural heterogeneity within and around plantations to enhance landscape connectivity and maintain avian functional diversity. This study provides the first empirical assessment of how cacay cultivation affects bird communities and offers guidance for balancing agricultural production with biodiversity conservation in the Orinoquía region.
Abstract Birds are a vital component of urban biodiversity worldwide, yet accurately measuring their abundance and diversity is challenging because most bird survey methods are not designed for highly urbanized environments. Surveys are often limited to parks and other green spaces and are biased toward wealthier neighborhoods and high-income countries, hindering our understanding of how birds use all urban habitats. Our aim was to develop and evaluate an inclusive, global method for surveying urban birds across diverse city environments. We developed the Global Urban Bird Survey, a community-based method using acoustic recorders to inventory birds. Local experts trained and coordinated community members, who conducted repeated surveys in five cities between 2022 and 2024: Dakar (Senegal), Nairobi (Kenya), Rio de Janeiro (Brazil), Paris (France), and Toronto (Canada). Survey locations were selected via a stratified block-randomized design within city cores, ensuring unbiased coverage across urban habitats. We compared the performance of the Global Urban Bird Survey with eBird, a widely used source of community-science data, to assess species richness, occurrence, and spatial coverage. Acoustic surveys effectively captured urban bird diversity. eBird detected significantly higher mean species richness than the Global Urban Bird Survey in Dakar, Nairobi, Paris, and Rio de Janeiro, while no significant difference was observed in Toronto. However, eBird’s spatial coverage was substantially lower than that of the Global Urban Bird Survey, particularly in low-income cities, highlighting gaps in community-science datasets. The Global Urban Bird Survey provides a robust, scalable approach to monitoring urban avian biodiversity across a range of habitats and socioeconomic contexts. Broader, more representative sampling of urban environments is critical for understanding global patterns of biodiversity. Community-based acoustic monitoring complements existing community-science efforts, offering a valuable tool for inclusive conservation planning and informed urban biodiversity management worldwide.
Abstract Effective conservation efforts are contingent on understanding the underlying demographic processes that regulate wildlife populations. Productivity is a key driver of population growth, and in avian taxa, nest survival and clutch size dictate the number of chicks successfully hatched. Patterns in productivity can vary spatially and temporally, shaping populations and their evolutionary trajectories. We evaluated potential drivers of nest survival and clutch size in a declining, salt marsh specialist bird species, Rallus crepitans (Clapper Rail) using data from 2019–2021 modeled with a Bayesian logistic exposure model. Nest survival probabilities varied across sites and incubation stage, but vegetation thickness (visual obscurity) and the timing of nesting affected nest survival the most. Nest survival peaked in the middle of the breeding season, coinciding with an increase in clutch size and an apparent larger number of concurrent active nests. Despite tidal flooding, nest failures largely occurred due to predation, suggesting that the dilution effect in the mid-season coupled with thicker vegetation around the nest lead to the highest probability of nest success. Increases in clutch size during the periods of highest survival suggest adaptive timing in reproductive investment. Our findings highlight the importance of appropriately timing restoration and other vegetation management efforts in marshes to minimize impacts during the breeding season and provide a contemporary estimate of nest survival in this declining population.
