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Birds 2

Villager photo by Lorcan Otway

A mouse clutched in the talons of the Tompkins Square Park juvenile red-tailed hawk took a last look at the camera.

Park hawks could be at risk for fatal food poisoning

By Lorcan Otway

For the second year in a row, a juvenile red-tailed hawk has visited Tompkins Square Park in search of rodents and the occasional pigeon. It may well be that this young visitor is just what the neighborhood is seeking, since the park has had problems with rat infestation.

This year’s hawk is not the same one seen in the park last year. It is about a year old, the same age as the hawk from last year.

Tompkins Square has become a mecca for hawk watching. Most afternoons there is a gathering of photographers, heads tilted back, scouring the trees for sight of the raptor, also known as a chicken hawk. Playground moms hold up their camera phones. There is Dennis Edge, a devoted bird-watcher, with his long lens. There is Lincoln Karim, whose photos and blogging on Palemale.com advocate for the protection of these birds of prey from dangers ranging from kites left in trees to poison in the parks. There is Francois Portmann, a Swiss photographer, and local photographer and blogger Robert Arihood.

Arihood has written about the park’s rodent problem, but lately has focused on how eradicating the rats may be endangering the raptor. The hawkeyed photographer and others are concerned that rat poison may also be poisoning the hawks.

Villager photo by Sandy Hechtman

Early last month, a red-tailed hawk in Washington Square Park noshed on a squirrel.

Asked about poison being introduced into the park’s food chain, Gregory Gough, an avian ecologist at the Migratory Bird Center of the Smithsonian Institution in Washington, D.C., said it most likely would affect the juvenile red-tailed hawk.

“It can’t be good for him,” he said.

“You might try letting the hawk do the job himself; he can eat quite a lot of rodents,” Gough noted. He suggested the city curtail the poison program in Tompkins Square from November until mid-December, when it will become apparent whether the juvenile hawk has decided to become a permanent resident of the East Village. Mature hawks stake out permanent territory, while younger ones are migratory, seeking a spot to settle.

Difethialone is the rat poison being used in Tompkins Square Park. According to “Toxicology,” by G. D. Osweiler, Difethialone is a second-generation anticoagulant poison. It kills by causing internal hemorrhaging, usually after only a single ingestion.

In November’s first week, Difethialone packets were placed in rodent burrows in the park. A week later a young hawk was seen feeding on mice 10 feet from a sign warning of the poisoning. Ward B. Stone, a wildlife pathologist with the New York State Department of Environmental Conservation, has researched the subject and has found “anticoagulant rodenticides to be important secondary poison of raptors,” including, most prominently, red-tailed hawks and owls.

In March, San Francisco’s Department of the Environment issued a moratorium on use of so-called single-feed rat poisons after the death of three red-shouldered hawks in Golden Gate Park were attributed to them.

Chris Geiger, who manages San Francisco’s Integrated Pest Management Program, explained that these poisons were removed from the list of rodenticides approved for use on city property after the U.S. Environmental Protection Agency’s revised risk assessment for rodenticides recognized the danger of secondary toxic effects on raptors.

Villager photo by Sandy Hechtman

After the meal, another squirrel — a relative or friend of the deceased? — aggressively challenged the Washington Square raptor, but then retreated, perhaps fearing becoming dessert.

Michael Fry of the American Bird Conservancy feels Difethialone and similar poisons should never be used. He suggests a return to less-toxic, first-generation rodenticides, such as Chdrophacinome, Diphacinone and Warfarin. Fry explained that a rodent that eats either the first- or second-generation anticoagulants takes from four to seven days to die. During that time the animal might be eaten by a predator. In the case of a second-generation anticoagulant, a rat may have eaten the poison several times over a period of days, building up a super-lethal dose.

“The E.P.A. has put forward a mitigation plan, to take all the second-generation anticoagulants off the consumer market, allowing only first-generation anticoagulants to be sold over the counter,” said Fry. “We want the use of these second-generation anticoagulants to be restricted to indoor use alone.”

The New York City Parks Department has not totally ruled out using the extra-potent poisons said Jesslyn Tiao, a spokesperson.

“Rodent control involves education and eliminating food sources andharborage, in addition to using rodenticides,” Tiao said. “We follow the Department of Health’s rodenticide recommendations and primarily use products containing Bromadiolone, which has a lower secondary risk value than Difethialone. We occasionally use products containing Difethialone when other materials have not been effective. We monitor parks for rodent activity and only bait or trap in those areas where rats are present. When baiting we use minimal doses in a manner that minimizes the risk of secondary contact.

“If a hawk or owl is present we can suspend baiting until the predator moves on,” Tiao said. “Large open parks such as Central, Prospect or Van Cortlandt are more likely hunting grounds for predatory birds than places like Tompkins Square, where benches, fences, litter baskets, etc. provide cover for prey. So, we can’t simply say, no, we don’t use it, but we are aware of the issues and manage pesticide use responsibly.”

Asked if Parks would stop baiting a smaller park like Tompkins Square with Difethialone now that a hawk is hanging out there, Tiao said that’s correct.

“Yes, until it moves on,” she said. “We’re aware of the presence. We’re sensitive to that and we would suspend baiting for a while until it’s gone.”

With reporting by Lincoln Anderson

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