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Climate change could disrupt a critical fueling-up stage for migratory birds just as they’re preparing to depart on their autumn journeys to Central America, according to research published in the journal Ecology Letters.

Cornell Lab of Ornithology research ecologist Frank La Sorte developed computer models of predicted changes in climate for every week of the year in the Western Hemisphere.

Computer Modeling Predict Climate Change

These models were then overlaid with weekly estimates of abundance for 77 migratory bird species that fly between breeding grounds in North America and non-breeding grounds in Mexico and Central America.

La Sorte used bird observations from the eBird citizen-science database, an online program run by the Cornell Lab of Ornithology.

“Hotter” colors (red to yellow) on the map indicate a climate that will significantly change by 2100 compared to previous conditions during the last week of August

La Sorte’s research pinpointed a period in late summer in the temperate zone of North America when the climate is projected to be significantly different from the historical norm.

That change in climate, La Sorte says, could affect insect and plant communities, which in turn would threaten food resources for migratory birds during the crucial stage when they’re bulking up and layering on fat reserves to fuel their autumn migration journey.

Migratory Birds Most at Risk

Most at-risk, La Sorte says, would be eastern migratory birds that fly greater distances and require large fuel reserves, and the juvenile birds that just hatched a few months earlier and are undertaking their first migration—a hazardous journey that can be extremely energetically taxing.

The Scarlet Tanager is one of the species whose food supply could be impacted by projected changes in climate

“Using bird observations from eBird, our study provides an unprecedented level of spatial and temporal detail, allowing us to identify locations and times when migratory bird populations may be at particular risk under future climate change,” says La Sorte.

“This information is important because it advances our understanding of the unique challenges migratory birds are likely to face in the future, and where and when the application of conservation efforts may achieve the greatest benefits.”