Transcript:

HAWK MIGRATIONS: Red Tailed HawksHere's a program from our archives.ambience: red-tailed hawk callWe're listening to the call of the red-tailed hawk, one of the better-known birds of prey, or raptors, in the eastern United States. I'm Jim Metzner, and this is the Pulse of the Planet, presented by the American Museum of Natural History. This month, many birds, including raptors, are starting their migrations south, but the red-tailed hawks of New York City have other plans. DeCandido: The essential question of hawk migration is why. Certain individuals, such as the red-tailed hawks of New York City, don't go anywhere. Other birds, like warblers, go south, because their insects that they feed on are gone for the winter. Robert DeCandido is Chief Naturalist of New York City's Urban Park Rangers. His research has led him to conclude that food, not cold, causes hawks to migrate. DeCandido: We look at migration as something that is done in response to diminishing food concentration, and diminishing hours of hunting availability. So what's keeping red-tailed hawks in New York City? DeCandido: They're looking for a place where prey has an extreme concentration. So a place like Central Park, although one wouldn't think of it as wildlife habitat, is wonderful for hawks and other raptors during the winter. Because the prey populations -- the squirrels, the mice, the rats -- have built up to extraordinary levels during the summer. There are very few predators around here to take advantage of them at that time. Plus, you have all this food being transported in by people, that squirrels and rats and all the others get a hold of. So now their prey populations increase. The hawks migrating south are quick to spot this, so they stop and feed here for a while, until the prey populations crash or are no longer as abundant, and then they move on again. We've been listening to a program from our archives. If you want to hear more, check out our podcast. I'm Jim Metzner and this is the Pulse of the Planet.