Originally aired during the week of September 17, 2000
Hang gliders weighing hundreds of pounds with their gear can keep aloft for hours at a time by "thermals"--pockets of warm air rising into the atmosphere. These bubbles of warm air serve as invisible avenues for many birds of prey migrating south to tropical climes this time of year. Especially spectacular in mid-September is the flight of the broad-winged hawk, one of the most common hawks in the northeast. This hawk is a buteo--a raptor with long, broad wings and tailfeathers that soars gracefully in wide circles. About the size of large crow, the hawk can be found feeding in warm weather months near openings in the woods created by roads, trails, or wetlands. When the migration begins, observers at legendary hawk-watch sites like Hawk Mountain in Pennsylvania have seen thousands of broad-wings at once sailing on thermals. These updrafts carrying flocks of hawks are sometimes called "kettles."
Noisy flocks of geese overhead mark the passing of summer and the onset of a new season. On clear autumn evenings, you may also hear the twittering of night-migrating songbirds. The flight of the broad-winged hawk may be less obvious to us, but it's a pretty spectacular sight if you know where to look. Perhaps the most common of local hawks, broad-wings are leaving their northern breeding grounds in mid-September and making for the Florida Keys, southern Mexico, or the South American coast. As the morning sun warms the air, thermals--invisible bubbles of warm air--provide the lift the birds need to gain altitude. On a warm breezy day from early morning until early afternoon, you may even see several birds soaring together. Some really good observation points in Vermont include Mount Putney in the south and Mount Philo in the north.
In mid September, broad-winged hawks are beginning their annual migration to warmer climates. Later in the fall, the red-tailed hawk, another common raptor, is on the move. While many of this species migrate south in the fall, some of the birds are present in our area throughout the year. Red-tails usually do not begin breeding until their third year. Pairs build large stick nests near the top of trees at the edge of the woods. Two to four eggs are usually laid in the spring, hatching in about 30 days. Young remain near the nest until they can fly, then shadow their parents as they learn to forage for themselves. Red-tails feed on small rodents, rabbits, medium sized birds, and snakes. This hawk uses rising currents of warm air to glide up to lofty heights--it will soar from one thermal to the next, conserving energy as it follows the path of least resistance along its migratory route.
Buteos, like the broad-winged hawk, are birds built for soaring. They have long, broad wings and a short, fan shaped tail, and are a favorite sight of bird watchers observing the annual hawk migration. Accipiters, like the sharp-shinned hawk, live in forested areas and their wings are designed to zig-zag through trees. They have shorter, rounder wings with a long, rudder-like tail. When they migrate, they do a good deal more flapping than the buteos. Falcons make up the third grouping in the hawk family. These birds are made for speed, with long-pointed wings and a tapered tail. When migrating, they fly at treetop level, streaking across the sky. Often they will fly straight through thermals that transport other hawks on their long journey. The Peregrine is the swiftest of all falcons. They can hurtle down from their cliffside nests at speeds of 175-200 miles per hour!
Just a few decades ago, peregrine falcons were nearly wiped out due to widespread use of DDT and other chemical compounds used in agriculture. The chemicals caused peregrine females to lay thin-shelled eggs that had little chance of hatching. Thankfully, the DDT ban in 1972 and breeding programs by biologists have brought this magnificent bird back from the brink of extinction. Peregrines nest at the top of cliffs close to waterways where they hunt smaller birds. Among other places in the twin state area, nesting pairs of peregrines can be seen at the Fairlee, Vermont, Pallisades and Osceola East Peak in New Hampshire's White Mountain National Forest. Well-known for their aerial acrobatics and incredible speed, these birds are also hardy migrators. Canadian researchers recently tracked a peregrine that traveled over 300 miles a day on its autumn trip from Alberta to Veracruz, Mexico.
