Columbia resident Alisa Esposito , has about 353 purple martins in her freezer. The bodies are tagged and bagged and accompanied by notes on the time and date they were collected.
The dead birds were removed from the vicinity of the William B. Umstead Bridge to offer proof that the birds, a protected species, are being killed at the site, Esposito said. Working under the auspices of the U.S. Fish and Wildlife Service , she's coordinating a monitoring program to count dead purple martins at the bridge, which serves as a pre-migratory roost for the species.
The body count so far is about 596, Esposito said. Calling the number conservative, she noted that it doesn't include purple martins that may have fallen in the water, been eaten by scavengers or been carried off or crushed by vehicles.
With the numbers of the iridescent purple birds flocking at dusk estimated to be in the thousands, their descent to perch on the cable under the bridge has been likened to something out of an Alfred Hitchcock movie.
The data will be given to the North Carolina Department of Transportation.
"NCDOT said for anything to happen we need that data," said Keith Watson , migratory bird biologist with the U.S. Fish and Wildlife Service in Asheville .
Watson is overseeing the program for the agency, which is mandated to protect purple martins under the Migratory Bird Treaty Act .
"Providing the numbers that we're collecting this year will give our agency a reason to go to DOT and show them that there is a significant bird kill occurring on a structure that they are responsible for," he said. "Under the Migratory Bird Treaty Act, there's no provision to authorize a permit for killing birds on that bridge."
Volunteer Lincoln Larson , an intern with the Defenders of Wildlife red wolf outreach program, is monitoring the bridge in his free time. With hazard lights on and a portable yellow light provided by the Department of Transportation flashing from the top of the vehicle, he makes a round trip across the bridge to count dead birds around sunrise and sunset daily.
"At night it's much harder to see," he said. "I get the occasional person ask me if everything is OK."
"It's sort of difficult to do," said Clay Willis , environmental supervisor in Division I for the state Department of Transportation . "Fortunately there's not a whole lot of traffic on that bridge."
The Department of Transportation recently posted signs at each end of the bridge warning motorists of low flying birds at dusk. The signs will be in place from July through September.
"We were hoping that that would get people's attention," said Willis. Flashing lights on the signs were initially considered.
"They felt like, at that time, we didn't really have the numbers on the birds," said Willis. "The cost and maintenance on those lights is significant because they probably would have to be solar-powered-type lights. They're pretty expensive."
It was first thought that the birds, estimated to weigh approximately 2 ounces, were being struck only in the evening, thus the wording on the signs. But visits to the bridge this year have indicated that morning mortalities are occurring as the birds leave the roost each day.
"We've taken a video of the morning departure," said Esposito. "They are getting hit just as hard in the morning as the evening."
The bird count began July 1. But Esposito said that birds have been collecting there in large numbers for weeks.
"The roost has been active since June, with significant numbers coming to roost since approximately June 20th," she said in an e-mail. "About 2,000 birds were seen roosting on June 27th."
Concerned over the bird-traffic conflict, Esposito, who works with the endangered red-cockaded woodpecker for a local environmental consulting firm, spearheaded a meeting at the bridge last summer with the Transportation Department and Fish and Wildlife representatives.
The idea of using fencing to keep the birds from flying into traffic was raised. The federal fish and wildlife agency recommended putting up fencing on the western end of the bridge, where the birds roost.
Fencing has been used successfully in Texas and Louisiana, according to the Purple Martin Conservation Association . The Department of Transportation opted not to go the fencing route, citing cost, aesthetics and the bridge design as concerns and posted the warning signs instead.
Within an eight-week period, Esposito expects bird mortalities could be between 1,500 and 2,500.
"It's not even at the peak of the roost yet," she said.
Based on an estimate of regional fledges from her colony records, she believes that peak numbers should occur in late July this year.
Forming a pre-migratory roost is essential to the species, which includes fledglings . The birds are attracted to large bodies of water and open spaces. Water keeps them warm, and expansive locales offer safety from predators.
Local bird enthusiasts are working with fish and wildlife and the Purple Martin Conservation Association to prepare a proposal to present to state Sen. Marc Basnight, D-Dare.
"He wanted a proposal from the group to take to NCDOT," said Watson. It will include "a description of the problem, an estimate of the number of birds being killed, what's being done and why it hasn't worked and what you want them to do."
Watson said he hopes that the Transportation Department will become a co-leader in solving the issue. "It depends on how you want to approach it, legally or cooperatively," he said.
"It's an active situation," said Willis. "We're not ignoring it. And we are waiting to get these numbers. We want to try and find a reasonable solution."
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