Does Westchester County Airport threaten the American kestrel?

A bird sits atop a fence post as a jet plane takes off from Westchester County Airport, White Plains, N.Y., on Thursday. Recent data from the Federal Aviation Administration shows that over the past four years, the American kestrel, a small falcon, has been struck and killed 21 times by airplanes at Westchester County Airport. less A bird sits atop a fence post as a jet plane takes off from Westchester County Airport, White Plains, N.Y., on Thursday. Recent data from the Federal Aviation Administration shows that over the past four years, ... more Photo: Bob Luckey Jr. / Hearst Connecticut Media Buy photo Photo: Bob Luckey Jr. / Hearst Connecticut Media Image 1 of / 5 Caption Close Does Westchester County Airport threaten the American kestrel? 1 / 5 Back to Gallery

Development of open, grassy agricultural lands in the northeast is pushing the diminutive American kestrel to migrate to homes with much larger predators: airplanes.

The small falcon has been dubbed a species of special concern in Connecticut because of a loss of habitat and dip in population. Contributing to the problem could be the tendency of the birds to relocate to airports, where the flat, wide-open spaces resemble their destroyed homes.

The problem is particularly evident at Westchester County Airport, where 21 American kestrels were struck and killed by airplanes over the past four years, according to the Federal Aviation Administration. During that same time, planes in Connecticut hit a total of 22 kestrels.

The strategies that airports have in place to keep other birds, such as geese and starlings, away from airfields are less successful with the more intelligent American kestrel.

“The Northeast is one of the areas that show the steepest declines of the species. We don’t know exactly why this bird is in decline,” said Sarah Schulwitz, assistant director at the American Kestrel Partnership, which is leading a nationwide volunteer effort to count and gather data on the birds. “There so far has not been any rigorous scientific evidence to point to exactly why this is being seen.”

What they do know, Schulwitz said, is that kestrels seem to be dying as adults rather than ba bies.

“When there are chicks in the nest there is a pretty high chance of survival,” she said. “It looks like adult survival is being negatively impacted. It certainly isn’t helping the species that adults are dying at the airport.”

The American kestrel is both the smallest and most common falcon in North America. Its breeding range stretches from central Alaska across North America to Nova Scotia and south all the way to Mexico and the Caribbean.

In Connecticut, though, it is difficult to find any at all.

Ted Gilman, senior naturalist at Audubon Greenwich, said he doesn’t know where any are nesting in the area.

In 2002, the Department of Energy and Environmental Protection listed the kestrel as a threatened species in the state of Connecticut, deeming it “likely to become an endangered species within the foreseeable future throughout all or a significant portion of its range within the state,” according to the DEEP website.

In 2012 DEEP changed its classification from “threatened” to a “species of special concern,” which is less serious, but shows the birds are still thought to have a low population level in the state.

Peter Scherrer is the airport manager at Westchester County Airport. He said recorded bird strikes are up this year, but that’s because airport officials are getting better at recording collisions, not necessarily because more birds are being hit.

The airport works hard to monitor animals in the area, Scherrer said, and tries to educate pilots to report when they see a spot on their airplane after a flight. Often the spot, which those in the airline world call “snarge,” came from hitting a bird.

If it is a large bird that was hit, airport personnel can often identify it themselves, but when it’s a smaller bird they have to mail the remnants to Washington D.C. to be identified by a team at the Smithsonian.

Scherrer said as American kestrels hover looking for prey, they can get sucked up in wingtip vortices, circular patterns of air formed behind a wing as it generates lift, and smashed into the ground, killing them even if they are never actually struck by the plane.

The airport does have strategies to discourage birds from the area, including a “bird bomb” that makes loud noises to scare them off. Some birds, however, are easier to scare away than others.

Derek Colbert, a wildlife biologist who works at the airport, said some birds, particularly raptors like the American kestrel, get used to harassment techniques before they are driven away.

“They are some of the smarter birds we have in the field so they pick up more quickly the fact that it’s not actually a threat,” he said.

He said the state is working on a study to see if relocating birds from airports to other areas will keep them from coming back. His fingers are crossed that Westchester County will get to be a part of the study.

“At the end of the day we have great habitat here at Westchester County Airport for American kestrel,” Colbert said.

Erin Strasser, a biologist with the Bird Conservancy of the Rockies, said some people who live close to the airport could be harming the kestrels without knowing it. Across the nation many people have taken to setting up nesting boxes in their yards to help challenged species, such as the kestrel, rebound. Residents who live near airports might want to take down boxes that have housed the birds, she said.

Strasser said the deaths caused by air strikes could be having a large impact on the population, but it’s hard to say definitively.

Kevin McGowan, a professor at the Cornell Lab for Ornithology, said a lot of the things an airport needs to operate, such as runway markers, provide perfect perches for kestrels. He said identifying those perches and adding bird spikes could help the issue.

American kestrels only weigh about a quarter of a pound, but they can fly up to 39 mph. When they collide with an airplane during lift off, the plane takes up to 75 pounds of impact.

“Nobody wins when a kestrel is hit by a plane,” McGowan said. “It’s not good for the plane either. Bird strikes are a significant hazard to air travel.”

pfrissell@hearstmediact.com; @PeregrineFriss