The other morning I got off the Metro and watched a large flock of pigeons graze lazily in Farragut Park. They were joined on the ground by bold, well-fed house sparrows and European starlings. As I watched these birds lounge through the grass I thought: where are the predators?
It seems to me that cities are the perfect place for birds of prey. There is an abundance of food in pigeons and house sparrows, and there are plenty of concrete ledges for nest-building. Why, then, don't we see more birds of prey in DC?
My working theory was that crowded cities don't meet the territorial needs of raptors. Birds of prey can wage some epic battles over territory (ask Martha), and perhaps cities just don't provide enough room for the birds to...wait for it...spread their wings.
But I needed an expert opinion. I managed to get ahold of Mr. Brian Walton, one of America's foremost experts on birds of prey. Mr. Walton has a long history of protecting birds of prey, and has been the coordinator of the Santa Cruz Predatory Bird Research Group since 1977 and is a lecturer at the University of California - Santa Cruz.
I asked Mr. Walton specifically about Peregrine Falcons, here's what he had to say:
bDC: What are the territorial requirements of Peregrines?
Walton: "No specific requirements, they need a nest ledge, and abundant food which seems to be occurring in virtually all major cities. In places where food is extremely abundant they may nest as close as a hundred yards apart (in Long Beach Harbor there are 6 pairs less than a mile apart), and in some places they now nest on ground (saltmarshes) or even emergent tree snags in re-growing forests to exploit abundant food in those locations. "
bDC: Why more falcons haven't moved into cities like DC, despite the fact that there is an ample food source (pigeons and house sparrows by the thousands) and lots of buildings and ledges for nests?
Walton:"Many places where peregrines nest in cities, the original birds were released there. In other places peregrines have moved in and I do not think anyone knows why they have moved into those cities and not others. It may be a matter of time. I would expect some of the birds that nest on bridges around DC to move into the city soon, however the amount of human activity on some buildings can limit use by falcons. There are definitely many buildings of the type that one would expect peregrines to occupy in DC. There is definitely food and other needs."
"Peregrines are doing a pretty good job of occupying cities, they can because they only eat birds and bats that they catch in the air. Their prey seems to be vulnerable moving through the cities where there is no natural cover. Peregrines catch birds and bats at twilight and even after dark in city lights. Add to normal prey items is the abundant pigeon and other bird populations like sparrows, starlings and parrots. No other predatory bird can manage this lifestyle over the course of a year and most need very specific food items during the breeding season. Occasional red-tail, kestrel and in some areas merlins and coopers hawks can make a living but usually the prey for the types of other raptors is not sufficient or available in cities."
"One other thing to make clear about peregrines. They are not adapting to cities. They live and hunt in the air, they roost where it is safe, the buildings or bridges are just like cliffs, and in fact there are fewer eagles and owls to harass the falcons or eat their young in the city environment. They do the exact same thing in the city as their counterparts do in the wild areas. No other raptor could do the same in the city as they do in wild areas. "
So it sounds like once Peregrines and other raptors can develop appetites for city food, cities could be an ideal place for them to live. I hope that development comes sooner than later...those Farragut Park pigeons have had it too good for too long.