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Hawks Migrate Through Chincoteague Wildlife Refuge, Chincoteague, Virginia
October 6, 1997
They're soaring overhead--large birds weighing up to 9 pounds, with wing spans of up to 7 feet. These birds of prey, or raptors, include eagles, hawks, falcons, osprey, kites and other species. Thousands are migrating throughout North America right now. Yet, they will fly by unnoticed by most people.
Irvin has been observing and counting raptors at Chincoteague refuge for over 12 years. On a typical day during raptor migration, Irvin will count an average of 30 hawks, eagles, and falcons coming through the refuge per hour!
Chincoteague National Wildlife Refuge, is located on the eastern shore of Virginia, just south of Cape May, New Jersey. Why do you think so many raptors fly through this particular area?
A hint lies in the geography of the region. As explained in the September 15 Monarch Migration Update, Cape May serves as a funnel for migratory butterflies as well as for raptors, songbirds, shorebirds, and some waterfowl. Prevailing winds, which move in a northwest to southeast direction, tend to concentrate the migrants along the eastern seaboard. Then, they funnel into the Cape May peninsula and follow the coastline south--through Chincoteague National Wildlife Refuge and on to another funnel at Kiktopeake Point--en route to wintering grounds in the southeastern United States and Latin America.
A Predictable Parade
Over the years in which Irvin Ailes has been watching raptors at Chincoteague, he has also observed a distinct pattern in the arrival of the different species to the refuge. "First the Sharp Shinned Hawks and the American Kestrels come through, then the osprey, eagles, Coppers and Merlin hawks, Peregrine Falcons and Northern Harriers come. Why do you think raptors come in stages following this general pattern?
The following facts about raptors might give us some clues. First, remember that raptors are predatory birds. They live high on the food chain.. As fall advances, the food supply on their nesting grounds decreases forcing many to migrate.. In addition, because migration is hard work and requires food for fuel, the raptor must find food along the entire migratory route. What types of food are raptors eating during migration?
Food for the Road
Few researchers have investigated the relationship between predator and prey during migration. However, Frank Nicoletti of the Duluth Audubon Society, has made some fascinating observations while monitoring migration at Hawk Ridge in Minnesota. He has focused his research on the American Kestrel, a small raptor, as it migrates along the shore of Lake Superior.
Frank watched the Kestrels catching large numbers of dragonflies in mid-flight while both the Kestrels and the dragonflies were migrating along Lake Superior. While Kestrels also eat other insects, Frank thinks Kestrels might be timing their migration in sequence with the migration of dragonflies. His hypothesis is that, not only Kestrels, but other species of raptors too, might follow the prey most useful for fueling its migration.
Let's go back to Chincoteague to find out what the raptors are eating as they migrate through. Click Here to see a chart showing the prey each finds there. How might the availability of this prey change with the seasons? On the nesting grounds? Along the migratory trail?
Good Habitat Means Good Eating
The habitat at the refuge is managed with migrants in mind. For example, a fragrant coastal shrub called myrtle is planted and maintained to attract insects--food for warblers, swallows, and other songbirds. In turn, these small birds provide an important source of food for the medium-sized raptors such as Sharp-shinned and Coopers Hawks.
The Next Journey South Update Will be Posted on October 13, 1997.