Scientists Reveal ‘Leapfrog’ Migration in Golden Eagles

Posted by Jeff on Dec 10, 2015 @ 8:49 am in Conservation | 0 comments | Last modified: December 10, 2015

A bird with the wingspan of an NBA player seems like it’d be pretty hard to miss. Yet the iconic Golden Eagle has proved so elusive in eastern North America that scientists are only now defining its range and coming up with population stats in the region.

Todd Katzner, a research wildlife biologist at the U.S. Geological Survey, says there are a few thousand Golden Eagles that breed in remote portions of Canada—Quebec and Labrador—and winter in the Appalachian Mountains. His latest study, published today in The Condor: Ornithological Applications, shows that within this group, the eagles that breed the farthest north generally spend the winter farthest south, with some migrating all the way to Alabama and Georgia. In doing so, they “leapfrog” over the birds in the middle, which go only as far south as Pennsylvania and New York. (A few don’t even make it out of Canada.)

The study speculates that this leapfrog pattern is the result of a trade-off. Golden Eagles in Pennsylvania and New York, for instance, face harsher winters. But on the other hand, they have an easier migration and might also get the first crack at favorable breeding territories in the spring.

Eastern Golden Eagles are believed to be geographically and possibly genetically distinct from the much larger population of Golden Eagles that spans almost all of western North America. Before the 1930s scientists didn’t realize that this species lived in the East at all, and many birding field guides still don’t mention the smaller population.

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