Revival of falcons worries scientists Wildlife managers believe falcons may prey on other endangered birds.

April 01, 1992|By Bruce Reid | Bruce Reid,Staff Writer

A pair of endangered peregrine falcons appears to be trying to nest on a tall building in Ocean City. By itself, that would be more good news for the species once wiped out in the East by the pesticide DDT.

However, the birds have posed a difficult question for state wildlife managers: What if the falcons, which are not native to the Eastern Shore, start preying on declining numbers of native terns and other species state biologists are trying to protect?

The falcon, an impressive hunter with a wingspan of up to 44 inches, is a symbol of efforts to help predators rebound from poisoning by DDT. Peregrines nesting since the late 1970s on a high ledge on the U.S. Fidelity and Guaranty building in Baltimore have brought repeated attention to those efforts.

But some ornithologists have raised questions about whether the birds deserve to be favored over less glamorous but equally endangered species, such as terns and plovers.

Eirik A. T. Blom of Bel Air is one of a small number of ornithologists and others arguing that peregrines shouldn't be encouraged to nest along the mid-Atlantic Coast.

"This pair doesn't belong" in Ocean City, Mr. Blom, a chief consultant for the National Geographic Society's "Field Guide to the Birds of North America," said this week.

While a lot of money has been spent introducing captive-bred peregrines following a federal ban on DDT in the early 1970s, Mr. Blom said, "No one has spent a dime worrying about the effects of this on the environment."

Mr. Blom and others are worried that a large colony of royal terns, gull-billed terns, common terns, black skimmers and other "water bird" species could become peregrine prey or be harassed by the aggressive falcons.

Besides the peregrine pair on the USF&G building, on Light Street, six other pairs are known to have nested in Maryland last year, including one on the Chesapeake Bay Bridge and another on the Francis Scott Key Bridge.

The falcons in Maryland already are incubating eggs or will be any day, state officials said.

David F. Brinker, who studies populations of terns and similar species for the state Department of Natural Resources, said the water birds nesting on a sand spit and marshy area called the Fourth Street Flats, in Ocean City's Assawoman Bay, are carefully guarded against human intrusion. He said the state enlists a volunteer each year to keep boaters and others off the breeding area.

The flats are about two miles from where the peregrines appear to be trying to nest, or within the falcons' hunting range.

The 10 or so pairs of royal terns there last year were the only ones known to be nesting in Maryland, Mr. Brinker said. The state classifies royal terns as endangered. Gull-billed terns are classified as threatened in the state, as are black skimmers.

Even if the falcons don't prey on all species of water birds on the flats -- some may be too large -- peregrines could disrupt nesting by repeatedly frightening the terns and other species, Mr. Blom said.

Glenn Therres, supervisor of DNR's non-game and urban wildlife program, said yesterday that the peregrines are being neither encouraged or discouraged. The building where they have been roosting for several weeks does not have too many flat, protected ledges on which they could build a nest, he said.

Mr. Therres declined to say where the building is, only that it is north of the Fourth Street Flats. He said the owner did not want publicity about the falcons. Too many people trying to see the falcons could drive them away, he added.

"Essentially, what we're doing is letting the birds decide for themselves what they want to do," Mr. Therres said. If they are successful at nesting and officials find that the birds' eggs roll off the building, for example, state officials may consider providing a nest box, he said.

Also, biologists may consider discouraging the peregrines if they start preying on the water birds and harming the population, Mr. Therres said.

About two dozen peregrine pairs, with the aid of Cornell University and government agencies, are nesting along the East Coast from New Jersey to Virginia.

The restoration effort was concentrated on the coast, rather than the birds' traditional nesting range along inland rivers and in the mountains, for two reasons: Many young peregrines that ornithologists tried to establish in the inland areas were quickly killed by great horned owls, which do not inhabit the salt marshes on the coast. Also, remote coastal islands are good nesting sites because there isn't much human intrusion.

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