The study, published in the journal The Auk: Ornithological Advances showed that migrating birds travel faster in spring than in fall because arriving late to their breeding grounds can affect their reproductive success.
Past studies have shown that migrants take shorter breaks in spring, but it's harder to tell whether they also move faster in the air.
When the researchers used high-tech weather surveillance radars operated by the National Oceanic and Atmospheric Administration (NOAA) and the Department of Defense, US, on migrating birds, they found that birds indeed flew faster in spring and compensated more for crosswinds that could blow them off course.
"Many migration studies look at a few individuals, maybe on the scale of hundreds, but with radar, we're now documenting the behaviours of millions of individuals on a given night. That's a lot of data, and when you do see flight behaviour results that are regionally or seasonally different, it's quite compelling," said Kyle Horton, researcher at the University of Oklahoma.
The analysis reveals macroscale patterns in the aggregate behaviours of migrating birds that support existing literature on flight strategies of migrants.
In addition, the study makes new discoveries about greater overall wind compensation during spring and new hypotheses about the processes underlying these patterns.
The researchers hope that birds' ability to adjust their migratory behaviour for different conditions will buffer them against the effects climate change, which may cause large-scale shifts in wind intensity.
