Under future climate scenarios, changing winds may make it harder for North American birds to migrate southward in the autumn, but make it easier for them to come back north in the spring according to researchers from the Cornell Lab of Ornithology.

They came to this conclusion using data from 143 weather radar stations to estimate the altitude, density, and direction birds took during spring and autumn migrations over several years. They also extracted wind data from 28 different climate change projections in the most recent report from the Intergovernmental Panel on Climate Change (IPCC). Their findings were published in the journal Global Change Biology.

Lead author Frank La Sorte, a Cornell Lab of Ornithology scientist, and co-authors project that winds from the south are expected to become stronger by the end of the century during both spring and fall migration periods. Winds from the west may be stronger during spring migration and slightly weaker during the fall. Westerly winds are much more variable overall and harder to predict because they are tied to erratic fluctuations in the high altitude jet stream. Wind changes will be most pronounced in the central and eastern portions of the continent.

Future Wind-Aided Flight Changes

With an assist from stronger tailwinds during spring migration, birds would likely arrive in better condition on their northern breeding grounds with better odds of survival. Their fall migration flights into stronger headwinds would drain more energy. If headwinds are too strong, birds may choose not to fly at all on a particular night, throwing off the timing of their migrations.

Some birds may be able to adapt because the expected wind changes are likely to happen gradually. Studies also show that migratory birds already adjust their migration strategy under current conditions, altering their headings to compensate for winds that push them from their intended flight path.

Support for this study came from The Wolf Creek Charitable Foundation, Amazon Web Services, and the National Science Foundation.

Photo of Eastern Meadowlark by Laura Frazier, Cornell Lab of Ornithology; Graphic by Frank La Sorte, Cornell Lab of Ornithology.