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?
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 nearby 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.
The 10 or so pairs of royal terns in the area last year were the only ones known to be nesting in Maryland, said David F. Brinker, who studies populations of terns and similar species for the state Department of Natural Resources. The state classifies royal terns as endangered. Gull-billed terns are classified as threatened in the state, as are black skimmers.
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.
In Massachusetts last year, biologists were faced with a similar situation when a young, unpaired peregrine began preying on endangered roseate terns nesting on an island in Buzzards Bay. Within two weeks, the peregrine had devoured 35 roseate terns and 15 common terns. The falcon was captured and moved to another area.
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.