By Kim Van Fleet, IBA Biologist
From August through December tens of thousands of birds of prey (including 14 different species of hawks, falcons, and eagles and two species of vultures) pass through Pennsylvania on their annual southward migration. Some raptor species are short distance migrants; others travel thousands of miles to Central and South America. These birds have been following the same migration paths for eons, and the state's topography is conducive to migration movements. Consequently, Pennsylvania is a hotspot for raptor watching.
Fall migration occurs over an extended period of time; however, bald eagles, northern harriers, red-tailed hawks and golden eagles migrate throughout the entire season. Overall, each species tends to migrate within a certain time frame and experiences peak migration periods. Ospreys and broad-winged hawks are usually the first birds to migrate through Pennsylvania. Shortly thereafter American kestrels, merlins, and peregrine falcons start to move. By mid-September sharp-shinned hawks and Cooper's hawks are migrating through the region. In early October the red-shouldered hawk flight begins, followed closely by red-tailed hawk movements. By mid-October, vultures, rough-legged hawks, and northern goshawks can be observed. By mid to late October through early December golden eagles are observed in numbers.
Migrating raptors employ several types of flight strategies including soaring, gliding, and flapping, or combinations thereof. Flapping expends the greatest amount of energy while soaring/gliding requires less work but increases travel time. Soaring/gliding is often employed earlier in the season when thermal production is high. Thermals are pockets of warm air that form when the sun strikes the earth, causing a warmed bubble of air to rise. Migrating raptors find these thermals and soar upward on pockets of air. After reaching the top, birds glide until they catch another thermal. By late October through December thermal production sharply decreases, and migrating raptors employ a combination of gliding and/or flapping.
The long linear mountains of the Ridge and Valley Province and Allegheny Front Area of the Appalachian Plateau Province are oriented so that winds striking the ridges produce updrafts that facilitate soaring/gliding flight. As a result, migrating raptors often concentrate along the ridges and are able to travel with minimal energy expenditure. Wind speed also contributes to the strength of lift. If winds are calm or light, little ridge lift will develop. On the other hand, if winds are too strong the updrafts become too turbulent to negotiate.
A number of PA ridges are Important Bird Ares (IBAs) due to the role they play in raptor migrations. IBAs with established hawk watch sites include Kittatinny Ridge at Waggoner's Gap (Cumberland Co.) and Hawk Mountain Sanctuary (Berks Co.), Second Mountain (Fort Indiantown Gap, Dauphin Co.), Tuscarora Mountain at "The Pulpit" (Franklin Co.) and the powercut along the ridge top at State Game Lands (SGL) #88 on the Perry/Juniata Co. border, Stone Mountain (Rothrock State Forest, Mifflin/Huntingdon Co.), Tussey Mountain (on the powercut west of Route 26 Huntingdon/Centre Co. line), Bald Eagle Ridge, and Audubon Pennsylvania's newest IBA, The Allegheny Front (Allegheny Front hawk watch, Bedford Co.). One site with very easy access that isn't an IBA but still bears mention is the Jack's Mountain Hawk Watch on Jack's Mountain (Mifflin Co.) where state route 4007 (Wills Road) crosses the ridge.
Tips for Hawk Watching:
- If you plan to go for a day take a lunch and beverages (a thermos of soup or hot beverage is great on a cold day).
- Many watch sites lack restroom facilities, so check with the watch site leader for more information. You can get contact information at www.HMANA.org
- Dress appropriately and layer your clothing. Ridge tops are always several degrees cooler and winds are stronger. Don't forget a hat and gloves.
- Wear warm/sturdy shoes or boots for hiking or sitting. Sites with trail access include Waggoner's Gap (short trail), Hawk Mountain Sanctuary (long trail), Stone Mountain (long trail). Tussey Mountain (moderately long trail), and Allegheny Front (short trail). Take a pad to sit on.
- A few sites (including "The Pulpit or SGL #88 on Tuscarora Mountain, Second Mountain, and Jack's Mountain) can accommodate car-side watching.
- Take binoculars and/or spotting scope and a field guide.
- Many of the watch sites are manned by friendly folks who are happy to answer your questions, but please wait for lulls in the flight before asking questions.