Falcons Trading Wild Life for Urban Perches
Sunday, April 16, 2006
Stephanie R. Spears leaned over the side of the Woodrow Wilson Bridge with a video camera as the drawspan opened to let a construction barge pass through. Spears, an environmental specialist with the bridge replacement project, was looking for the pair of peregrine falcons nesting there when suddenly one of them came after her.
The shrieking bird with a sharp beak and hooked talons shot into the air, wheeled around and dived. "Watch your head!" Spears shouted to a handful of onlookers just as the female falcon veered away. Peregrines are said to be the fastest birds on Earth, capable of diving at 200 mph. This one was protecting three eggs.
The eggs are on a jumble of powdery road grit inside one of the bridge's concrete supports, only a few feet down from the rumble and shake of thousands of vehicles a day crossing between Maryland and Virginia. "It's an interesting place to make a nest," Spears said. "It's probably why she gets nervous when we stop traffic -- it's so quiet."
The Wilson Bridge is a dangerous place for a bird, but more of the region's peregrines are nesting on bridges, skyscrapers or other manmade structures than on the mountain cliffs that are their natural homes. Falcons are living on more than a dozen bridges in Maryland and Virginia and have made nests on tall buildings in Baltimore and Richmond.
The falcons' willingness to live near people and noise has let them thrive in an urban region. But it has frustrated state wildlife biologists who have tried in vain to get them to nest in the back country.
It is harder for a falcon to make a living on a mountain than in an urban area, said researcher Shawn Padgett. "They can't just take a plunge off a bridge and get a starling going by," he said. "They have to go out and hunt."
The Wilson Bridge peregrines, like the bald eagles that have a nest near the bridge, have an avid fan club. Paula Sullivan of Alexandria visits Jones Point Park on the Alexandria shoreline several times a week to watch the peregrines through a spotting scope and to trade stories about them with people fishing there.
"The first time I saw the bird come in with prey, it really screamed -- I assume to announce its arrival," she said. "Feathers were flying in all directions. My assumption was that it was a pigeon. . . . It's really thrilling. I've gotten such an enormous kick out of it."
This is the second year that peregrine falcons have nested on the 55-foot-tall bridge. This year's eggs are due to hatch early next month. The birds laid eggs last year that vanished -- taken, Spears thinks, by raccoons.
Spears has seen raccoons walking the girders under the existing bridge and says they could use the span to traverse the Potomac -- just like humans. In many ways, the bridge is a miniature ecosystem of predators and prey. Pigeons and rats live there. Waterfowl linger under it, and gulls fly over it to scout for trash.
Construction workers on the bridge being built near the existing one have not found where the raccoons live, but they have learned to lock up their food after the creatures broke into their lunchboxes to eat their sandwiches. The raccoons have left their distinctive paw prints -- the front one resembling a human hand and the rear one a footprint -- in fresh concrete on the new bridge.
Life on the bridge meets the falcons' three basic needs: a rough surface with good drainage to lay their eggs, a high perch from which to hunt and a good food supply of other birds. The Wilson Bridge peregrines often sit atop 200-foot-tall construction cranes, even riding them as the cranes move along the Potomac River by barge. The falcons have made a noticeable dent in the bridge's pigeon population, but they also grab gulls and songbirds.