<< Back 9/4/02 The Naturalist's Corner By Don Hendershot The daytime skies over the eastern U.S. are filling to capacity as millions of broad-winged hawks begin their annual southerly trek to Central and South America. The skies begin to fill in Canada and New England in early August and become more crowded as the mass exodus picks up steam and fellow pilgrims from the great lakes, the northeast and the mid-Atlantic states join in. Then, as quickly as it started, it’s over. By the end of September there is hardly a broad-winged left in North America. They have squeezed through the narrow Mexican corridor, where hawk watchers in places like Cardel in Veracruz report as many as 1.7 million broad-wings. While some of these migrants might overwinter in south Florida and/or the Keys, most spend the winter from Mexico south through Costa Rica and Panama and on to Colombia. Broad-wings and other raptors are diurnal migrants because they depend primarily on thermals; rising columns of hot air created as the sun warms the earth. When the birds find a thermal they begin to spiral slowly upward, soaring on the warm air currents. Broad-wings and other raptors keep an eye out for thermals and if they see other birds catching a lift, they will quickly join them. It is believed that broad-wings can see thermals from as far away as six miles. So a thermal could actually sweep up hawks along a 12-mile corridor. Groups of raptors in a thermal are called kettles. Kettles may range in size from a few birds to a thousand or more. Kettle is a descriptive term. The birds appear to boil or bubble upwards until the reach the top of the thermal and spill out. The tops of some of those thermals may be as much as three miles high. When the birds reach the top of the thermal they stream out on rigid, swept-back wings and glide for miles (depending on the height of the thermal and conditions) in a southerly direction. When they lose momentum, they begin to scan the horizon looking for the next thermal or updraft to send them on their way. As massive as this event is, with literally millions of birds soaring, kettling, and streaming through the daylight hours, it went virtually unnoticed until the mid 1930s. The parade moves south quickly and most birds pass through any given site within a week. The migration for the most part follows an inland path along rugged mountain terrain where updrafts help move the kettles along. Kettles are also often so high that they are difficult to see, even with binoculars. However in certain hotspots like Hawk Mountain in Pennsylvania there was a group of people who knew of this time when the winds carried hawks by the thousands. Hunters would line the ridge tops and by day’s end, untold thousands of dead hawks would litter the ground and be left to rot. In 1934 the Emergency Conservation Committee of New York headed by Rosalie Edge leased the property and created Hawk Mountain Sanctuary. Hawk Mountain became the first refuge for migrating birds of prey and today boasts the longest and most complete record of raptor migration in the world. Other things happened in the mid-30s to shed light on this annual aerial display. Seven and 8x binoculars from Germany began to fill the hands of birdwatchers in the states, drawing those dark specs from the wild blue yonder into view. Petersen’s field guides hit the markets in 1934 and these specs became identifiable. Today people still line the ridges at Hawk Mountain and other places like Hawk Ridge Nature Preserve in Minnesota, but with binoculars and spotting scopes instead of 12-gauge shotguns. Broad-wings number in the hundreds of thousands at these spots and others across the country. But migrating raptors are pretty exciting, even in smaller numbers. There are several hawkwatches within a three- to four-hour drive from WNC and most are always looking for volunteers to help monitor the site. Pilot Mountain State Park near Pinnacle, N.C., averages about 5,000 raptors a year between Aug. 15 and Nov. 15. For more information contact Toby Gordan at 336.325.2704. Nearby Mount Pisgah Overlook along the Blue Ridge Parkway is manned as often as possible during the fall from September to October. For more information on Mount Pisgah contact Bill Sanderson at 828.298.2752. One of the most prolific raptor migration sites in the area is Caesars Head State Park in South Carolina. Caesars Head is located just south of Brevard on U.S. 276. It is manned by park staff and volunteers from late August through December and generally records around 12,000 raptors, with broad-wings making up the great majority. To contact Caesars Head call 864.836.6115. While broad-wings make up the greatest percentage of birds in the east, hawkwatchers also get looks at red-tails, sharp-shinned and Cooper’s hawks as well as bald eagles, ospreys, peregrine falcons, American kestrels, turkey vultures and the occasional rarity like a golden eagle or northern goshawk. (Don Hendershot can be reached at don@smokymountainnews.com)