Recovering After Ban on DDT Use, Osprey Find Urban Waters Good Fishing
BABY BIRD BOOMLET
NEW YORK — A15-KNOT sea breeze blows across Jamaica Bay. With its five-foot wingspan, an osprey is using the breeze to hover over the shallow water. Suddenly, the bird drops 15 feet into the bay and emerges with a winter flounder in its talons.
What makes this event noteworthy is that the osprey is fishing in New York City waters. In the background is the World Trade Center. Close by is a subway line.
This year in the bay, three pairs of nesting osprey produced a total of three young birds. ``I've found no breeding record of osprey in New York City this century,'' says Don Riepe, chief ranger at the Jamaica Bay Wildlife Refuge Center.
As is evident from the osprey in Jamaica Bay, in the 22 years since DDT has been banned, ospreys have made a steady comeback. From Maine to Florida, from the Great Lakes to Shelter Island, N.Y., the bird count is steadily rising. In 1967, the Audubon Society found only two nesting pairs of osprey in Rhode Island. That year, there were no fledglings in the state. Biologists found that the birds were absorbing the DDT from their fish diet. The DDT inhibited the bird's production of calcium, necessary for strong eggshells. The weakened eggs collapsed under the incubating bird.
But this year Rhode Island's Department of Environmental Management surveyed 49 nests and found 44 young birds. The state considered the season to be a success, although there was no increase in fledglings over last season.
The birds have also made a significant comeback in eastern Long Island. Before the use of DDT, there were 300 active nests on Gardiners Island, a large private island between the north and south forks of Long Island. By the late '60s, there were only about 20 active nests. Now, there are over 70 nests on the island.
Osprey lovers helped the birds recover by building wooden platforms on telephone poles for the birds to nest on. ``These artificial nesting platforms made a big difference in bringing the osprey back,'' says Alan Poole, managing editor of the Birds of North America project.
Despite the improvement, ornithologists doubt the bird will ever return to the pre-DDT levels. ``There has been a lot of overfishing of the waters, especially the menhaden,'' says Dennis Puleston, a naturalist who first uncovered the link between DDT and the birds. Today, he says the birds eat sea robins and flounder, which are harder to catch than menhaden, also called bunker. Bunker, an oily fish, have long been used for fertilizer.
Mr. Poole worries that the birds may be starting to reach their maximum population for the habitat they live in. He notes that the population growth rate has leveled off as the birds have been forced to nest in more-urban areas where they face such predators as raccoons and horned owls, which eat their eggs. In Rhode Island, for ex-ample, the growth rate has been steady for the past three seasons.
Part of the growth slowdown might be the result of bad siting of the platforms. Poole says that although utility companies are eager to help with the birds, the companies sometimes place the poles in poor locations. ``There can be a danger to the platforms,'' says Poole, who believes there should be some form of regulations on how and when the platforms should be erected.
The platforms, he explains, should be built on islands or over the water, since raccoons don't swim. They should also be out in the open, since osprey like to have a clear view of the surrounding area and prefer to nest away from trees and forests.
Although the osprey are picky about nesting sites, they are not bothered by civilization. For example, on Shelter Island, there is an active nesting platform on the side of a causeway. Cars, bicycles, and even dogs don't bother the birds.
In Jamaica Bay, part of the Gateway National Recreation Area, the osprey not only look out over the New York skyline, but they also are within a few miles of John F. Kennedy International Airport with the sounds of jets landing and taking off. ``The birds acclimate - it becomes background noise,'' Mr. Riepe explains.
The birds have had to adapt, because they have been steadily migrating west - towards more urban areas. For example, osprey have recently moved to Oyster Bay, which is heavily used by recreational boaters. This summer at least five osprey have been spotted looking for fish among the sailboats moored in the bay.
Two young osprey have built a nest on a platform erected several years ago in a marsh in Bayville by the Mill Neck Rod & Gun Club. ``It's the first time that platform has been used,'' says Jim Carroll, a member of the club. Next March, when the adult birds return from their migration to Brazil, they are likely to return to the nest where they will try to raise their own chicks within sight of New York City.