Invisible superhighways. That’s one way to describe the rising air currents that will whisk raptors through central Pennsylvania during this season’s migration. Golden Eagles, attuned to the subtle relationships between topography and wind, will scan our state’s prominent ridges and deep valleys as they soar southward as they have for millennia.
Golden Eagles are vaguely similar in appearance to the Bald Eagle. They are roughly the same size and shape, averaging about 10 pounds, measuring some 30 inches from beak to tail with a wingspan of 6 1/2 feet or more. Just as Bald Eagles take their name from the feathers of their prominent crown (bald derives from a Middle English word for white), so do Golden Eagles, with head and nape, whether juvenile or adult, covered by tawny plumes. Both are safeguarded by the federal Bald and Golden Eagle Protection Act. From there, the similarities end. Bald and Golden Eagles belong to different genera, meaning scientists hardly consider them cousins. Bald Eagles are indigenous to North America, while Golden Eagles additionally are found in skies throughout Europe and Asia. Bald Eagles scavenge quite a bit; Golden Eagles hunt terrestrial and winged prey. While Bald Eagles actively nest in Pennsylvania, Golden Eagles quietly pass through, drifting overhead in the spring as they move into breeding territories in northern Canada and breezing through in the fall as they follow ridgelines and strong winds toward more hospitable climes. In recent years, volunteer birders and curious onlookers have begun to take note of their passage, helping to count the eagles and other raptors as they stream by.
The closest reliable site near Pittsburgh for spotting Golden Eagles in migration is the Allegheny Front, about an hour and a half east. In a good fall season, several hundred are clocked passing the high scarp, providing stunning eye-level views of these birds in flight. Last year two Golden Eagles were captured there by scientists from the National Aviary and Powdermill Avian Research Center using a baited bow trap, a net secured to a bow-shaped rib that harmlessly springs over the bird like a wide hinge closing. The eagles were fitted with Platform Transmitter Terminals, small satellite backpacks that pinpoint their location.
Information from the transmitters reveals the ancient sky routes Golden Eagles fly and helps scientists consider where birds and people might come into conflict. Specific concerns exist with Pennsylvania’s developing wind farm industry. Seven wind farms are on line, and more are on the way. The research results may enable us to create nonpolluting, sustainable energy and protect the Golden Eagles’ flight paths. In the western U.S., where tall towers and spinning blades kill dozens of Golden Eagles annually, the interactions have not been good. Learning from those mistakes and proceeding carefully might allow Pennsylvania to get it right, for eagles and those who stand in awe of their long-evolved wanderings.
The National Aviary (www.aviary.org), Powdermill Avian Research Center, and the Pennsylvania Game Commission (www.pgc.pa.gov) have joined to study Golden Eagle migration in our region; visit their websites for regular updates. In addition to Golden Eagles, 15 raptor species use this same migratory superhighway.