Raptor Migration

A view of the study site where migrating Golden Eagles were  counted in autumn, looking southwest across the Copper River Valley. Photo courtesy of Carol McIntyre

A view of the study site where migrating Golden Eagles were  counted in autumn, looking southwest across the Copper River Valley. Photo courtesy of Carol McIntyre

During the months of September and October, the Wrangell Mountains Center is hosting a series of blog posts about raptors in partnership with the NEA and Copper River Valley’s Big Read. This year’s Big Read book is the Maltese Falcon by Dashiell Hammett.  So far we have explored raptors found in the Copper River Valley, falcons in particular, and what it is like to work with and rehabilitate raptors. This week we will take a deeper look into raptor migration and hear from Dr. Carol McIntyre, bird biologist for the National Park Service.

Migration is defined as the seasonal movement of animals from one region to another. Many, but not all, of diurnal raptors migrate in the spring and the fall. They spend summer nesting and raising young in Alaska and travel to warmer climates during the winter. Raptor migration is not completely understood and people like Carol are studying it today. Scientists are working to understand how many birds migrate through a given area, which may indicate their population size, as well as where those birds go, and what factors influence migration. Since the Copper River watershed covers an immense area in eastern interior Alaska, a substantial number of migratory birds, including raptors, travel through the region in spring and fall. Carol notes that the Wrangell-St. Elias National Park and Preserve, and the Copper River Valley, are home to one of the largest migratory bird flyways in Alaska and perhaps North America.

Raptor migration is an amazing event to witness: if you are in the right place on the right day you may be able to count hundreds of eagles and hawks flying overhead. Migrating diurnal raptors include Golden and Bald Eagles, Osprey, Northern Harriers, Sharp-shinned Hawks, Northern Goshawks, Red-tailed Hawks, Rough-legged Hawks, American Kestrels, Merlins, Peregrine Falcons, Gyrfalcons, and Swainson’s Hawks. You can learn more about these birds on Hawkwatch’s website

Photos of traveling by dogsled through the Mentasta Mountains and counting migrating eagles. Photos courtesy of Carol McIntyre

Carol’s recent work focuses on Golden Eagles. Tracking data for radio-tagged Golden Eagles indicate two broad Golden Eagle migration corridors in the Copper River Valley. One spanning the Mentasta Mountains south across the upper Copper River Valley to the northern slopes of the Wrangell Mountains; and a second spanning from the southern slopes of the Wrangell Mountains south across the Chitina River to the northern slopes of the Chugach. Carol said that they decided to count eagles in the Mentasta Mountains because she had data showing that many eagles from Denali travel through that region in the spring and fall, and that local birders had witnessed amazing numbers of eagles traveling though the area in early March. Carol and her husband spent their spring vacation in March 2014 traveling around the Mentasta Mountains by dog sled, camping out, and staying put for periods of time to count birds.

Carol McIntyre and her colleague at the US Fish and Wildlife Service, Stephen Lewis, recently published a study in the Journal of Raptor Research documenting large numbers of Golden Eagles migrating through the Mentasta Mountains in both spring and fall. In October 2014, during 39.5 hours of counting, they measured 1364 migrating eagles, as well as a number of other migrating raptors including 525 Rough-Legged Hawks.

McIntyre and Lewis note that there is not very much ecological and demographic information about most species of raptors nesting in interior and northern Alaska. Studies and counts, like the one just published, suggest that there are probably more migratory birds than previously thought. The paper notes that Alaska’s migratory Golden Eagles cross many ecological and political boundaries during their annual cycle. As the landscape around us changes it is important to understand how populations of migrating birds are affected. Studies like this are the first step, but there is a lot more to be learned.

You can read the full article by McIntyre and Lewis in the Journal of Raptor Research here

You can see raptors migrating through the Copper River Basin in the autumn when they are heading south from early September – late October, and in Spring from mid March – late May. Another great place to watch raptor migration is at Gunsight Mountain on the Glenn Highway

Posted on October 15, 2016 .