Migration on the Mountain
3/8/15
By David Brown
Every year in late February a ritual begins. Cars park at a gravel lot at the top of a mountain road. Individuals bundled in multiple winter jackets hike two-thirds of a mile along a snowy trail through the woods to a powerline cut to sit on a pile of rocks. They face southwest and scan with binoculars over the trees in front of them and over the valleys to the sides. This scene occurs daily on Tussey Mountain near State College and the participants are hawkwatchers looking for raptors migrating to northern breeding grounds. Their main interest is a dark-brown bird with a flash of gold and a seven-foot wingspan: the golden eagle.
Bald eagles are now a common sight year-round in Pennsylvania, but golden eagles are only found here in the winter months with their fall migration peaking at the beginning of November and their spring migration peaking the first three weeks of March. Golden eagles do not breed in Pennsylvania, so any dark eagles seen in the summer are almost certainly immature bald eagles. The name golden eagle comes from the gold feathers on the head and neck. Golden eagles have relatively small heads compared to bald eagles giving them a different flight silhouette. The white on the underside is also more cleanly organized than on immature bald eagles. The best way to learn to separate them is by going hawkwatching to get experience seeing both species.
Hawk Mountain Sanctuary is the best known site in Pennsylvania for fall raptor migration, but Tussey Mountain claims the title of spring golden eagle capital of the east. In 2008, Tussey Mountain set the spring record east of the Rocky Mountains with 62 golden eagles recorded in a single day, contributing to a total of 225 golden eagles for that year's spring count. Raptor migration extends through April as later migrating species such as osprey and broad-winged hawk pass through. Last year, from late February to late April, Tussey Mountain counted nearly 2400 raptors, of which over 200 were golden eagles.
The number of raptors seen on a given day is largely dependent on the weather. Raptors migrate using external lift to save energy. In early spring this lift can come from wind hitting the side of mountains and being directed upwards. At Tussey Mountain, warm winds from the south and southeast are ideal for these ridge updrafts. In late spring, sunny days will cause strong thermals that can lift the raptors out of sight.
For beginner hawkwatchers in the area, Tussey Mountain is a good place to start. The full-time counter and other experienced hawkwatchers can help locate and identify raptors. The only essential equipment is a pair of binoculars. More information on the Tussey Mountain hawkwatch can be found at http://www.tusseymountainspringhawkwatch.org/. For close looks at captive raptors, stop at the nearby Shaver's Creek Environmental Center.
Tussey Mountain is not the only place to see migrating raptors. Scan along the top of local mountains or simply look up once in a while from your backyard and you'll be surprised how much passes over otherwise unnoticed. Keep your eyes to the skies and I'll meet you on the mountain.
