Connectivity is key for birds that migrate both short- and long-distance. While it may seem like species that can fly should have less trouble moving through the landscape, migratory birds still need reliable stopover sites, intact breeding or non-breeding grounds, and flyways that are clear of threats.
Bird migratory routes are threatened by both climate change and land use change, two of the biggest drivers of biodiversity loss today. Many studies have looked at the pieces of this puzzle: how climate change impacts migratory connectivity, or how land use change impacts connectivity, for one bird species or a similar group of species. However, putting all these pieces together can create an integrated and more accurate picture of how migratory connectivity for multiple species is threatened by multiple risks, and where the biggest regions of concern are.
Saunders, S.P., DeLuca, W.V., Bateman, B.L., Deppe, J.L., Grand, J., Knight, E.J., Meehan, T.D., Michel, N.L., Seavy, N.E., Smith, M.A. and Taylor, L. 2025. Multispecies migratory connectivity indicates hemispheric-scale risk to bird populations from global change. Nature Ecology & Evolution. DOI: 10.1038/s41559-024-02575-6.
A new study provides this framework by using movement data collected from over 300,000 migratory birds across 112 species that breed in North America but migrate throughout the Western Hemisphere. This information was combined with data on climate change and land use change to create a multi-species, multi-threat approach to assessing the risk of migratory bird population declines, many of which include species of conservation concern. This provided an overall assessment of which species and which regions in the study area are most at risk in terms of connectivity.
The results show that of the 921 connections assessed, 59 were considered very high risk, and another 29 had high values for multiple risk components. Over half of the very high risk connections included breeding regions in the eastern U.S., with the New England/mid-Atlantic Coast accounting for almost a quarter of them. This region is expected to undergo substantial change in both temperature and land cover, and is connected to many species’ non-breeding grounds that are under climate change threat, such as the Bahamas.
Connections between Canada and South America were at the greatest risk, mostly because of high number of species that use them and the high conservation vulnerability of many of those species. Birds that move between these regions undertake some of the longest distance migrations in the Western Hemisphere, exposing them to numerous threats along the flyway. This emphasizes the importance of transboundary collaboration that is crucial to protecting long-distance connections whose interdependency is not always obvious.
The framework not only highlights specific regions that could be targeted for conservation efforts aimed at creating protected networks, but also provides a method for understanding spatial and seasonal variations across a large number of species. Migration is a critical component of many species’ lives, and using large-scale, multi-species analyses can lead to better decisions about how to best protect and conserve them. Maintaining connectivity, whether on the land, in the air, or across the water, ensures that populations can best respond to changes in the future.
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