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At least 991 records · Page 55Linked to original sources

USGS2023

Body size predicts the rate of contemporary morphological change in birds

Across the globe, bird morphology is changing rapidly. Although trajectories of change are frequently consistent across studies, rates of change among species vary in magnitude—a phenomenon that remains unexplained. By analyzing two independently collected datasets demonstrating consistent changes in morphology in 129 species, we show that rates of phenotypic change are negatively correlated with body size—that is, smaller birds are changing faster. Why smaller-bodied species are changing faster is unknown, but we found little support for the hypothesis that generation length explains variation in the rates of change. Rather, body size appears to be a primary mediator of species’ phenotypic responses to contemporary climatic change and should be considered when testing hypotheses about the drivers of change.

Proceedings of the National Academy of Sciences (P↗

USGS1998

Higher temporal variability of forest breeding bird communities in fragmented landscapes

Understanding the relationship between animal community dynamics and landscape structure has become a priority for biodiversity conservation. In particular, predicting the effects of habitat destruction that confine species to networks of small patches is an important prerequisite to conservation plan development. Theoretical models that predict the occurrence of species in fragmented landscapes, and relationships between stability and diversity do exist. However, reliable empirical investigations of the dynamics of biodiversity have been prevented by differences in species detection probabilities among landscapes. Using long-term data sampled at a large spatial scale in conjunction with a capture-recapture approach, we developed estimates of parameters of community changes over a 22-year period for forest breeding birds in selected areas of the eastern United States. We show that forest fragmentation was associated not only with a reduced number of forest bird species, but also with increased temporal variability in the number of species. This higher temporal variability was associated with higher local extinction and turnover rates. These results have major conservation implications. Moreover, the approach used provides a practical tool for the study of the dynamics of biodiversity.

Proceedings of the National Academy of Sciences↗

USGS1991

Great lakes embryo mortality, edema, and deformities syndrome (glemeds) in colonial fish-eating birds: Similarity to chick-edema disease

Several species of colonial fish-eating birds nesting in the Great Lakes basin Includ-ing herring gulls, common terns and double-crested cormorants, have exhibited chronic impairment of reproduction. In addition to eggshell thinning caused by high levels of DDT and metabolites, the reproductive impairment is characterized by high embryonic and chick mortality , edema, growth retardation, and deformities, hence the name Great Lakes embryo mortality , edema, and deformities syndrome (GLEMEDS). The hypothesis has been advanced that GLEMEDS in colonial fish-eating birds resembles chick-edema disease of poultry and has been caused by exposure to chick- edema active compounds that have a common mode of action through the cytochrome P-448 system. Detailed evidence has been collected from the following three groups of studies on herring gulls in the lower Great Lakes during the early 1970s; Forster’s terns in Green Bay, Wisconsin in 1983; and double-crested cormorants and Caspian terns in various locations in the upper Great Lakes from 1986 onwards. It has proved difficult to establish not only the onset of the disease in the various species at various locations but also the period in which chick-edema active compounds were released. Anecdotal evidence suggested that serious egg mortality . © 1988 by Hemisphere Publishing Corporation.

Illinois, Indiana, Michigan, Wisconsin, Minnesota,↗

USGS2020

Daily nest predation rates decrease with body size in passerine birds

Body size evolution is generally framed by the benefits of being large, while costs are largely overlooked. An important putative cost of being large is the need to extend development periods, which should increase exposure to predation and potentially select against larger size. In birds, this selection pressure can be important because predation is the main source of offspring mortality and predators should more readily detect the larger nests associated with larger body sizes. Here, we show for diverse passerine birds across the world that counter to expectations, larger species suffer lower daily nest predation rates than smaller species. This pattern is consistent despite latitudinal variation in predation and does not seem to reflect a tendency of larger species to use more protected nests or less exposed nest locations. Evidence instead suggests that larger species attack a wider array of predator sizes, which could reduce predation rates in nests of large-bodied species. Regardless of the mechanism, the lower daily nest predation rates of larger species yield slightly lower predation rates over the entire development period compared with smaller species. These results highlight the importance of behavior as a mechanism to alter selection pressures and have implications for body size evolution.

The American Naturalist↗

USGS2025

A flexible framework for N-mixture occupancy models: Applications to breeding bird surveys

Estimating species abundance under imperfect detection is a key challenge in biodiversity conservation. The N -mixture model, widely recognized for its ability to distinguish between abundance and individual detection probability without marking individuals, is constrained by its stringent closure assumption, which leads to biased estimates when violated in real-world settings. To address this limitation, we propose an extended framework based on a development of the mixed Gamma-Poisson model, incorporating a community parameter that represents the proportion of individuals consistently present throughout the survey period. This flexible framework generalizes both the zero-inflated type occupancy model and the standard N -mixture model as special cases, corresponding to community parameter values of 0 and 1, respectively. The model’s effectiveness is validated through simulations and applications to real-world datasets, specifically with 5 species from the North American Breeding Bird Survey and 46 species from the Swiss Breeding Bird Survey, demonstrating its improved accuracy and adaptability in settings where strict closure may not hold.

Biometrics↗

USGS2000

Nesting habitat and reproductive success of southwestern riparian birds

Vegetation structure and floristic composition strongly influence the structure of bird communities. To assess the influence of vegetation and other environmental characteristics on songbirds, we quantified nest-site characteristics and reproductive success of a riparian songbird community in Arizona. Although we found interspecific variation in characteristics associated with nest sites, we identified two suites of species that chose sites with similar characteristics. These “nest groups” were explained largely by nest height and characteristics of nest trees. Overall, nest success was low for songbirds in this community, and averaged 23%. The most common cause of nest failure was predation (81%), although brood parasitism by Brown-headed Cowbirds ( Molothrus ater ) was highest at nests of Bell's Vireos ( Vireo bellii ) (29%). No vegetation or environmental features were associated with the likelihood of cowbird parasitism for any species; nest success for Bell's Vireos was negatively associated with the amount of netleaf hackberry ( Celtis reticulata ) in the understory. Arizona sycamore ( Platanus wrightii ) and netleaf hackberry trees contained 41% and 17% of all nests, respectively, and therefore provide critically important nesting substrates for birds in this rare yet diverse vegetation community.

Arizona↗

USGS2002

Composition of cavity-nesting bird communities in montane aspen woodland fragments: The roles of landscape context and forest structure

We compared cavity-nesting bird communities in aspen ( Populus tremuloides ) woodland fragments classified on the basis of vegetation structure (tree density) and landscape context (surrounding vegetation). We found very few cavity nesters in fragments predominantly surrounded by forests. Fragments adjacent to meadows contained more species and a greater abundance of cavity nesters. Species richness and abundance were higher in sparsely than in densely treed meadow fragments. Because secondary cavity nesters are often limited by cavity availability, we augmented natural cavities with nest boxes. Although only five boxes contained bird nests, these were all in sparse aspen fragments predominantly surrounded by meadows. However, we found 25 northern flying squirrel ( Glaucomys sabrinus ) nests in boxes, none of which were in sparse meadow fragments. In addition to high-lighting the importance of landscape context in avian and mammalian habitat relationships, our results suggest that predator or competitor interactions may help structure this cavity-nester community.

Utah↗

USGS2020

At the end of the road: Lessons learned from comparing model- and design-based approaches to estimate population sizes of boreal birds in Alberta, Canada

Estimating population abundance is a challenging task complicated by the amount, type, and quality of available data. Conservationists have relied on design-based estimates from Partners in Flight (PIF), which primarily uses roadside data from the North American Breeding Bird Survey (BBS) to estimate populations sizes. However, the BBS was not designed to estimate population sizes. We developed models incorporating land cover and climate variables based on roadside and off-road point-count surveys. We calculated spatially explicit, model-based population estimates for 81 landbird species in Bird Conservation Region 6 in Alberta, Canada, and compared these to PIF estimates. We also developed a framework to evaluate how the differences between the detection distance, time-of-day, roadside count, and habitat representation adjustments explain discrepancies between the two estimators. We showed that the key assumptions of the PIF population size estimator were commonly violated in this region, and the two approaches provided very different population size estimates for most species. The average differences between estimators were explained by differences in the detection distance and time-of-day components, but these adjustments left much unexplained variation among species. Differences in the roadside count and habitat representation components explained most of the among-species variation. The variation caused by these factors was large enough to change the population size ranking of the species. The roadside count bias needs serious attention when roadside surveys are used to extrapolate over off-road areas. Habitat representation bias is likely prevalent in regions sparsely and non-representatively sampled by roadside surveys, such as the boreal region of North America, and thus population size estimates for these regions need to be treated with caution for certain species. Model-based integration of available data sources and additional sampling can contribute towards more accurate population size estimates for conservation in remote areas of North America.

Alberta↗

USGS2019

The relative importance of wetland area versus habitat heterogeneity for promoting species richness and abundance of wetland birds in the Prairie Pothole Region, USA

Recent work has suggested that a tradeoff exists between habitat area and habitat heterogeneity, with a moderate amount of heterogeneity supporting greatest species richness. Support for this unimodal relationship has been mixed and has differed among habitats and taxa. We examined the relationship between habitat heterogeneity and species richness after accounting for habitat area in glacially formed wetlands in the Prairie Pothole Region in the United States at both local and landscape scales. We tested for area–habitat heterogeneity tradeoffs in wetland bird species richness, the richness of groups of similar species, and in species’ abundances. We then identified the habitat relationships for individual species and the relative importance of wetland area vs. habitat heterogeneity and other wetland characteristics. We found that habitat area was the primary driver of species richness and abundance. Additional variation in richness and abundance could be explained by habitat heterogeneity or other wetland and landscape characteristics. Overall avian species richness responded unimodally to habitat heterogeneity, suggesting an area–heterogeneity tradeoff. Group richness and abundance metrics showed either unimodal or linear relationships with habitat heterogeneity. Habitat heterogeneity indices at local and landscape scales were important for some, but not all, species and avian groups. Both abundance of individual species and species richness of most avian groups were higher on publicly owned wetlands than on privately owned wetlands, on restored wetlands than natural wetlands, and on permanent wetlands than on wetlands of other classes. However, we found that all wetlands examined, regardless of ownership, restoration status, and wetland class, supported wetland-obligate birds. Thus, protection of all wetland types contributes to species conservation. Our results support conventional wisdom that protection of large wetlands is a priority but also indicate that maintaining habitat heterogeneity will enhance biodiversity and support higher populations of individual species.

North Dakota, South Dakota↗

USGS2026

Incorporating location uncertainty improves inference with stop-level North American Breeding Bird Survey data

Ecological models should account for uncertainty to be most effective and useful. Yet, uncertainty from model covariates—unlike that from other sources, such as sampling error or process variability—is seldom explicitly incorporated. This can cause underestimates of uncertainty to cascade through model parameter estimates, predictions, and downstream uses. Burner et al. proposed a method for quantifying uncertainty in covariates and incorporating it into models using informative Bayesian priors. This method was applied to stop-level Breeding Bird Survey (BBS) analyses, where land cover uncertainty at each stop arises from substantial stop location uncertainty. A limited validation of model-estimated land cover, using stops with known locations, indicated the method’s potential effectiveness, but it was not rigorously evaluated. We conduct a robust simulation-based test, generating stop locations, extracting land cover, and simulating bird communities across 210 BBS routes in the upper Midwest. We compare 3 models: a “known” model with true land cover, a “naive” model assuming consistent 800-m stop spacing, and a “full” model using informative priors to estimate land cover. Species parameter estimates and predicted prevalence patterns across gradients in land cover from the full model approached those of the known model and were substantially closer to the true values used in simulations relative to those from the naive model. Naive model parameters were more biased relative to the other models, and credible intervals of predicted species prevalence rarely included the true simulated values. The full model also produced land cover covariate estimates closer to true simulation values relative to the mean informative priors. Our results show that, for the BBS, informative priors enable more accurate stop-level analyses despite location uncertainty. In contrast, naive models that ignore this uncertainty yield poor inferences. More broadly, we demonstrate empirically the utility of informative priors to account for covariate uncertainty in ecological models.

Michigan, Minnesota, Wisconson↗

USGS2020

Crossroads of highly pathogenic H5N1: overlap between wild and domestic birds in the Black Sea-Mediterranean impacts global transmission

Understanding transmission dynamics that link wild and domestic animals is a key element of predicting the emergence of infectious disease, an event that has highest likelihood of occurring wherever human livelihoods depend on agriculture and animal trade. Contact between poultry and wild birds is a key driver of the emergence of highly pathogenic avian influenza (HPAI), a process that allows for host-switching and accelerated reassortment, diversification and spread of virus between otherwise unconnected regions. This study addresses questions relevant to the spillover of HPAI at a transmission hotspot: what is the nature of the wild bird-poultry interface in Egypt and adjacent Black Sea-Mediterranean countries and how has this contributed to outbreaks occurring worldwide? Using a spatio-temporal model of infection risk informed by satellite tracking of waterfowl and viral phylogenetics, this study identified ecological conditions that contribute to spillover in this understudied region. Results indicated that multiple ducks (Northern Shoveler and Northern Pintail) hosted segments that shared ancestry with HPAI H5 from both clade 2.2.1 and clade 2.3.4 supporting the role of Anseriformes in linking viral populations in East Asia and Africa over large-distances. Quantifying the interface between wild ducks and H5N1-infected poultry revealed an increasing interface in late winter peaking in early spring when ducks expanded their range before migration, with key differences in the timing of poultry contact risk between local and long-distance migrants.

Virus Evolution↗

USGS2018

State‐space modelling of the flight behaviour of a soaring bird provides new insights to migratory strategies

Characterising the spatiotemporal variation of animal behaviour can elucidate the way individuals interact with their environment and allocate energy. Increasing sophistication of tracking technologies paired with novel analytical approaches allows the characterisation of movement dynamics even when an individual is not directly observable. In this study, high‐resolution movement data collected via global positioning system (GPS) tracking in three dimensions were paired with topographical information and used in a Bayesian state‐space model to describe the flight modes of migrating golden eagles ( Aquila chrysaetos ) in eastern North America. Our model identified five functional behavioural states, two of which were previously undescribed variations on thermal soaring. The other states comprised gliding, perching and orographic soaring. States were discriminated by movement features in the horizontal (step length and turning angle) and vertical (change in altitude) planes and by the association with ridgelines promoting wind deflection. Tracked eagles spent 2%, 31%, 38%, 9% and 20% of their daytime in directed thermal soaring, gliding, convoluted thermal soaring, perching and orographic soaring, respectively. The analysis of the relative occurrence of these flight modes highlighted yearly, seasonal, age, individual and sex differences in flight strategy and performance. Particularly, less energy‐efficient orographic soaring was more frequent in autumn, when thermals were less available. Adult birds were also better at optimising energy efficiency than subadults. Our approach represents the first example of a state‐space model for bird flight mode using altitude data in conjunction with horizontal locations and is applicable to other flying organisms where similar data are available. The ability to describe animal movements in a three‐dimensional habitat is critical to advance our understanding of the functional processes driving animals’ decisions.

Functional Ecology↗

USGS2013

Estimating transmission of avian influenza in wild birds from incomplete epizootic data: implications for surveillance and disease spreac

Estimating disease transmission in wildlife populations is critical to understand host–pathogen dynamics, predict disease risks and prioritize surveillance activities. However, obtaining reliable estimates for free-ranging populations is extremely challenging. In particular, disease surveillance programs may routinely miss the onset or end of epizootics and peak prevalence, limiting the ability to evaluate infectious processes. We used profile likelihood to estimate the force of infection (FOI) in a low pathogenic avian influenza virus (LPAIv) epizootic model from censored time series of LPAIv prevalence in hatch-year waterfowl (order Anseriformes) at postbreeding and migration sites in North America. We found a mean LPAIv FOI of 0·12 day −1 [95% CI, 0·00–0·39], corresponding to an incidence rate of 0·11 day −1 , with geographic heterogeneity (min–max: 0·02–0·23 day −1 ) among study sites. These high infection rates indicate that most hatch-year waterfowl are likely infected with LPAIv early in the fall migration. Comparison of model-predicted and observed immunity confirmed our assumption of naïve hatch-year waterfowl and suggested long-term immunity (>6 months) for adults. Using the mean LPAIv incidence rate, we predict a shorter and lower epizootic curve for highly pathogenic avian influenza virus (HPAIv; 5 weeks with peak prevalence of 28% and 30% mortality) than LPAIv (8 weeks with peak prevalence of 50%). These findings indicate it is harder to detect HPAIv than LPAIv with swabs from live birds, which are commonly used during disease surveillance. Synthesis and applications . Our study highlights the potential of integrating incomplete surveillance data with epizootic models to quantify disease transmission and immunity. This modelling approach provides an important tool to understand spatial and temporal epizootic dynamics and inform disease surveillance. Our findings suggest focusing highly pathogenic avian influenza virus (HPAIv) surveillance on postbreeding areas where mortality of immunologically naïve hatch-year birds is most likely to occur, and collecting serology to enhance HPAIv detection. Our modelling approach can integrate various types of disease data facilitating its use with data from other surveillance programs (as illustrated by the estimation of infection rate during an HPAIv outbreak in mute swans Cygnus olor in Europe).

Journal of Applied Ecology↗

USGS2014

Consequences of habitat change and resource selection specialization for population limitation in cavity-nesting birds

Resource selection specialization may increase vulnerability of populations to environmental change. One environmental change that may negatively impact some populations is the broad decline of quaking aspen Populus tremuloides , a preferred nest tree of cavity-nesting organisms who are commonly limited by nest-site availability. However, the long-term consequences of this habitat change for cavity-nesting bird populations are poorly studied. I counted densities of woody plants and eight cavity-nesting bird species over 29 years in 15 high-elevation riparian drainages in Arizona, USA. I also studied nest-tree use and specialization over time based on 4946 nests across species. Aspen suffered a severe decline in availability over time, while understorey woody plants and canopy deciduous trees also declined. The decline of plants resulted from increased elk Cervus canadensis browsing linked to declining snowfall. Woodpeckers exhibited very high specialization (>95% of nests) on aspen for nesting, and densities of all six species declined with aspen over time. Mountain chickadees Poecile gambeli and house wrens Troglodytes aedon exhibited increasingly less specialization on aspen. Chickadees strongly increased in density over time, despite a relatively high specialization on aspen. House wren densities declined moderately over time, but nest-box addition experiments demonstrated that nest-site availability was not limiting their population. House wren densities increased with understorey vegetation recovery in elk exclosures via increased generality of nest-site use, demonstrating that the decline in understorey vegetation on the broader landscape was the cause of their population decline. Synthesis and applications . Management should target species that specialize in resource selection on a declining resource. Species with greater resource selection generalization can reduce population impacts of environmental change. Resource generalization can allow a species like the wren to take advantage of habitat refuges, such as those provided by the elk exclosures. Yet, resource generalization cannot offset the negative impacts of broad-scale declines in habitat quality on the landscape, as demonstrated by the general decline of wrens. Ultimately, aspen is an important habitat for biodiversity, and land management programmes that protect and aid recovery of aspen habitats may be critical.

Journal of Applied Ecology↗

USGS2015

Effects of wind-energy facilities on grassland bird distributions

The contribution of renewable energy to meet worldwide demand continues to grow. Wind energy is one of the fastest growing renewable sectors, but new wind facilities are often placed in prime wildlife habitat. Long-term studies that incorporate a rigorous statistical design to evaluate the effects of wind facilities on wildlife are rare. We conducted a before-after-control-impact (BACI) assessment to determine if wind facilities placed in native mixed-grass prairies displaced breeding grassland birds. During 2003–2012, we monitored changes in bird density in 3 study areas in North Dakota and South Dakota (U.S.A.). We examined whether displacement or attraction occurred 1 year after construction (immediate effect) and the average displacement or attraction 2–5 years after construction (delayed effect). We tested for these effects overall and within distance bands of 100, 200, 300, and >300 m from turbines. We observed displacement for 7 of 9 species. One species was unaffected by wind facilities and one species exhibited attraction. Displacement and attraction generally occurred within 100 m and often extended up to 300 m. In a few instances, displacement extended beyond 300 m. Displacement and attraction occurred 1 year after construction and persisted at least 5 years. Our research provides a framework for applying a BACI design to displacement studies and highlights the erroneous conclusions that can be made without the benefit of adopting such a design. More broadly, species-specific behaviors can be used to inform management decisions about turbine placement and the potential impact to individual species. Additionally, the avoidance distance metrics we estimated can facilitate future development of models evaluating impacts of wind facilities under differing land-use scenarios.

North Dakota, South Dakota↗

USGS2019

A network approach to prioritize conservation efforts for migratory birds

Habitat loss can trigger migration network collapse by isolating migratory birds’ breeding grounds from non-breeding grounds. Theoretically, habitat loss can have vastly different impacts depending on the site’s importance within the migratory corridor. However, migration network connectivity and the impacts of site loss are not completely understood. Here we used GPS tracking data from four bird species in the Asian flyways to construct migration networks, and proposed a framework for assessing network connectivity for migratory species. We used a node removal process to identify stopover sites with the highest impact on connectivity. In general, migration networks with fewer stopover sites were more vulnerable to habitat loss. Node removal in order from the highest to lowest degree of habitat loss yielded an increase of network resistance similar to random removal. In contrast, resistance increased more rapidly when removing nodes in order from the highest to lowest betweenness value. We quantified the risk of migration network collapse and identified crucial sites by first selecting sites with large contributions to network connectivity, and then identifying which of those sites were likely to be removed from the network (i.e., sites experiencing habitat loss). Among these crucial sites, 42% were not designated as protected areas. Setting priorities for site protection should account for the site’s position within the migration network, rather than only site-specific characteristics. Our framework for assessing migration network connectivity enables site prioritization for conservation of migratory species.

Conservation Biology↗

USGS2019

Fire disturbance influences endangered Cape Sable Seaside Sparrow (Ammopiza maritima mirabilis) relative bird count

Periodicity of fire disturbance is a known driver of ecosystem function and is reported as important in both promoting and maintaining viable breeding habitat for the endangered Cape Sable Seaside Sparrow ( Ammospiza maritima mirabilis ; CSSS). In south Florida, the CSSS serves as a fine-scale indicator of the marl and mixed-marl prairie communities of the Florida Everglades. The CSSS distribution is affected by numerous well-documented physical drivers, including water depth and fire regime. Here, we fit zero-inflated negative binomial generalized linear mixed models and used model selection to determine the relationship between CSSS bird count observations from 1992 to 2014 and the spatially-specific fire return interval on the landscape. CSSS bird count was highest at a 5–8-year fire return interval and increased linearly with the percent of cell burned (400 × 400 m cells). The results of this study can inform management plans designed to maintain existing, and promote new, marl prairie habitat for conservation of the CSSS.

Florida↗

USGS2021

Temperature‐associated decreases in demographic rates of Afrotropical bird species over 30 years

Tropical mountains harbor globally significant levels of biodiversity and endemism. Climate change threatens many tropical montane species, yet little research has assessed the effects of climate change on the demographic rates of tropical species, particularly in the Afrotropics. Here, we report on the demographic rates of 21 Afrotropical bird species over 30 years in montane forests in Tanzania. We used mark–recapture analyses to model rates of population growth, recruitment, and apparent survival as functions of annual mean temperature and annual precipitation. For over one‐half of focal species, decreasing population growth rates were associated with increasing temperature. Due to the trend in temperature over time, we substituted a time covariate for the temperature covariate in top‐ranked population growth rate models. Temperature was a better explanatory covariate than time for 6 of the 12 species, or 29% of all focal species. Population growth rates were also lower for species found further below their elevational midpoint and for smaller‐bodied species. Changes in population growth rates were more closely tied to changes in recruitment than to changes in apparent survival. There were no consistent associations between demographic rates and precipitation. This study demonstrates temperature‐associated demographic impacts for 6 (29%) of 21 focal species in an Afrotropical understory bird community and highlights the need to incorporate the impacts of climate change on demographic rates into conservation planning across the tropics.

Global Change Biology↗