William V. DeLuca

Each year, migratory birds move thousands of kilometres across international borders to track optimal environmental conditions. How tightly annual-cycle events are linked and how much flexibility exists in migration schedules will determine how vulnerable migratory birds are to environmental change. Using a global tracking database, we reconstructed full annual-cycle schedules of 2,324 individuals from 83 species. We found strong temporal links during autumn and spring migrations: departure from the breeding grounds predicted arrival at the non-breeding grounds and vice versa. During both migration periods, late-departing individuals shortened migration duration, but still arrived later than early-departing individuals. By contrast, arrival at and departure from the non-breeding grounds were not correlated, suggesting a temporal reset that buffered earlier delays. Despite resetting during the non-breeding period, migratory schedules remain globally interconnected, such that disruptions in one season can propagate to subsequent stages of the annual cycle, with consequences for migratory species and the ecosystem functions they support.

Conserving migratory birds effectively requires full annual cycle strategies that identify where on-the-ground efforts can have the greatest impact. Here, we present a hemispheric spatial framework to identify priority areas for 112 migratory bird species across the Americas. Building on full annual cycle prioritizations, we defined finer-scale spatial planning units that reflect differences in migratory and congregational behaviors between shorebirds and landbirds. We compiled population data for each planning unit and focal species and applied conservation planning tools to design area-efficient portfolios of sites and landscapes that secure 10% of each species’ population within the Americas’ flyways. The resulting minimum area portfolios include 175 shorebird sites and 80 landbird landscapes optimized to meet the species-specific 10% representation targets across breeding, non-breeding, and passage seasons. We also identified a broader set of complementary solutions, ranked by an importance score, to provide decision-makers with flexible options for strategic resource allocation. This framework provides the scientific foundation for the Americas Flyways Initiative (AFI), which aims to catalyze investment in nature-based solutions and bird-friendly infrastructure to enhance the conservation of migratory birds and strengthen the resilience of the Americas’ flyways by 2050.

Despite recent avian research describing major migratory pathways and stopover regions, many species-specific migratory pathways and stopover locations remain unidentified and uncharacterized. We selected 4 Nearctic–Neotropical migrant bird species experiencing population declines and for which targeted conservation is limited during migratory periods: Cardellina canadensis (Canada Warbler), Setophaga cerulea (Cerulean Warbler), Vermivora chrysoptera (Golden-winged Warbler), and Hylocichla mustelina (Wood Thrush). In three phases, we delineated species-specific migratory pathways with movement tracking data and eBird Status and Trends products (Phase I), identified species-specific stopover landscapes within migratory pathways with eBird Status and Trends products (Phase II), and characterized multi-species stopover hotspots within stopover landscapes with land use/land cover covariates (Phase III). Phase I revealed that 3 species (S. cerulea, V. chrysoptera, and H. mustelina) crossed the Gulf of Mexico via a more easterly pathway during post-breeding migration and a more westerly pathway during pre-breeding migration. In contrast, C. canadensis went around the Gulf of Mexico, while also avoiding the core Prairie Pothole Region and remaining in forested landscapes within the aspen parkland ecotone of southern Canada. In Phase II, forested landscapes predicted to support higher stopover use included major river valleys, the Appalachian Mountains, the northeastern United States, southern Ontario in Canada, and the Central American Highlands. In Phase III, we selected 2 case studies for characterization of predicted stopover habitat use and protected area status. Likely stopover areas near Huntsville, Alabama, USA, occurred in deciduous broadleaf forests away from developed land, while in northern Nicaragua near Ocotal, likely stopover areas occurred in premontane and montane tropical forests. Opportunities for conservation action were presented in both case studies, where all stopover use areas contained larger proportions of unprotected land. Moving forward, our flexible three-phase analytical approach provides the tools to support single- and multi-species conservation strategies.

Human activities have profound impacts on ecological systems and biodiversity worldwide. Estimating wildlife response to those activities across broad spatial scales is challenging, yet effective conservation measures require an understanding of where and when these activities are contributing to population declines. We investigated the relationship between exposure to human activities (conservation challenges) and population trends of migratory warblers (Parulidae) that breed in the United States and Canada. Our four‐stage approach (1) summarizes the literature describing the sensitivity of species to conservation challenges; (2) estimates weekly species' exposure across the full annual cycle; (3) quantifies spatial correlations among species' exposure to conservation challenges; and (4) quantifies the relationships between seasonal exposure to conservation challenges and warbler population trends. Exposure during post‐breeding migration, followed by the stationary non‐breeding season and pre‐breeding migration, explained the most variation in warbler population trends. Within the post‐breeding migratory season, the conservation challenges with the greatest total seasonal exposure values were roads, light pollution, communication towers, forest management, and livestock management. During this season, species undergoing the steepest declines were associated with exposure to light pollution, communication towers, urban and suburban areas, livestock management, and agriculture. Notably, exposure to conservation challenges during the breeding season was not an important predictor of warbler population trends. Our results provide hemispheric, full annual cycle information for prioritizing conservation investments and additional research for warblers, specifically the importance of addressing challenges to which birds are exposed during post‐breeding migration. More broadly, this framework can be used to assess spatiotemporal conservation challenges impacting migratory species trends globally.

A primary prediction of climate change ecology is that species will track their climate niche poleward and upslope. However, studies have shown species responding in surprising ways. In this study, we aim to understand the impact of global change on species ranges by considering both climate and habitat changes. Using occupancy analysis of acoustic survey data in the mountains of the northeastern United States, we tested specific predictions of range responses to warming (shifting upslope), precipitation change (shifting downslope), and forest composition change (shifting downslope). We found that American red squirrels Tamiasciurus hudsonicus, key nodes in northern North American food webs, are not tracking increasing temperatures upslope, despite substantial warming in recent decades. Structural equation modeling indicates that red squirrel abundance is primarily influenced by red‐spruce forest cover, which has shifted downslope with recovery from historical logging and acid deposition. Accounting for the multiple dimensions of global change will enable better predictions and more effective conservation strategies.

Global agreements to reduce the extinction risk of migratory species depend critically on intersecting migratory connectivity—the linking of individuals between regions in different seasons—and spatial patterns of environmental change. Here we integrate movement data from >329,000 migratory birds of 112 species to develop a parameter representing exposure to global change: multispecies migratory connectivity. We then combine exposure with projected climate and land-cover changes as a measure of hazard and species conservation assessment scores as a metric of vulnerability to estimate the relative risk of migratory bird population declines across the Western Hemisphere. Multispecies migratory connectivity (exposure) is the strongest driver of risk relative to hazard and vulnerability, indicating the importance of synthesizing connectivity across species to comprehensively assess risk. Connections between breeding regions in Canada and non-breeding regions in South America are at the greatest risk, which underscores the particular susceptibility of long-distance migrants. Over half (54%) of the connections categorized as very high risk include breeding regions in the eastern United States. This three-part framework serves as an ecological risk assessment designed specifically for migratory species, providing both decision support for global biodiversity conservation and opportunities for intergovernmental collaboration to sustain migratory bird populations year-round.

Aim: Spatiotemporal variation in resource availability is a strong driver of animal distributions. In the northern hardwood and boreal forests of the northeastern United States, tree mast events provide resource pulses that drive the population dynamics of small mammals, including the American red squirrel (Tamiasciurus hudsonicus), a primary songbird nest predator. This study sought to determine whether mast availability ameliorates their abiotic limits, enabling red squirrel elevational distributions to temporarily expand and negatively impact high‐elevation songbirds.Location: Northeastern United States.Methods: We used two independent datasets to evaluate our hypotheses. First, we fit a dynamic occupancy model using data from camera trap surveys to evaluate red squirrel distributional responses to pulses in the tree mast. We also assessed population responses using systematic auditory surveys analysed with an open‐population binomial mixture model. Further, we used modelled red squirrel abundance in nest‐survival models to evaluate whether their abundance is correlated with the daily nest survival of three songbird species.Results: The tree mast provided a critical resource pulse that resulted in a two‐fold increase in the annual elevational distribution of red squirrels. The elevational distribution of red squirrels ranged from a minimum of ~450 m (range: 663–1145 m asl) following two consecutive years without a masting event to a maximum of over 1000 m (range: 443–1545 m asl) after a large mast event. The daily nest survival of three songbird species tended to decline with an increase in the abundance of red squirrels.Main Conclusions: Tree mast is a central biological phenomenon in many temperate and boreal forests. This study reveals how this resource pulse results in range changes in a small mammal that is both a seed and bird predator, as well as prey for many carnivores. Thus, understanding this phenomenon can inform the conservation and management of northern forests, including breeding songbirds.

The conservation of migratory birds poses a fundamental challenge, their conservation requires coordinated action across the hemisphere, but those actions must be designed and implemented locally. To address this challenge, we describe a multilevel framework for linking broad‐scale, full annual cycle prioritizations to local conservation actions for migratory birds. We developed hemisphere‐scale spatial prioritizations for the full annual cycle of migratory birds that breed in six different ecosystems in North America. The full annual cycle prioritizations provide a hemispheric context within which regional priorities can be identified. Finer resolution, regional prioritizations can then inform local conservation actions more effectively. We describe the importance of local conservation practitioner contributions at each level of the process and provide two examples of regional spatial prioritizations that were developed to guide local action. The first example focused on coastal North and South Carolina, USA, and used information on marsh birds, shorebirds, ecological integrity, and co‐benefits for people to identify Cape Romain, South Carolina as a high‐priority site for conservation action. The second example in Colombia used information on migrant and resident birds to identify the Cauca Valley as a high‐priority site. The multilevel conceptual framework we describe is one pathway for identifying sites for implementation of local conservation actions that are guided by conservation priorities for migratory birds across their full annual cycle.

The conservation of migratory birds poses a fundamental challenge: their conservation requires coordinated action across the hemisphere, but those actions must be designed and implemented locally. To address this challenge, we describe a multi-level framework for linking broad-scale, full annual cycle prioritizations to local conservation actions for migratory birds. We developed hemisphere-scale spatial prioritizations for the full annual cycle of migratory birds that breed in six different ecosystems in North America. The full annual cycle prioritizations provide a hemispheric context within which regional priorities can be identifieed. Finer resolution, regional prioritizations can then inform local conservation actions more effectively. We describe the importance of local conservation practitioner contributions at each level of the process and provide two examples of regional spatial prioritizations that were developed to guide local action. The fierst example focused on coastal North and South Carolina, USA, and used information on marsh birds, shorebirds, ecological integrity, and co-benefiets for people to identify Cape Romain, South Carolina as a high-priority site for conservation action. The second example in Colombia used information on migrant and resident birds to identify the Cauca Valley as a high priority site. The multi-level conceptual framework we describe is one pathway for identifying sites for implementation of local conservation actions that are guided by conservation priorities for migratory birds across their full annual cycle.