Spring Means Nesting Time for Urban Birds
Spring means nesting time for birds, and urban birds are no exception. Birds’ nests can be found in surprising places throughout the city, from skyscraper window ledges, to store awnings, to the Jamaica Bay Wildlife Refuge. The city’s house sparrows often nest in the ends of traffic light poles. An imported species, like starlings, they also take over the nests of native bird species such as New York’s state bird, the eastern bluebird.
Nesting behavior is different for each species. Almost every kind of bird builds its own style of nest structure, which has evolved depending on the birds’ size, behavior, habitat, brood size, vulnerability to predators, and other factors. A few, such as the brown-headed cowbird, lay their eggs in other birds’ nests, while others take over the abandoned nests of other species. For example, bluebirds, house wrens, starlings, tree swallows, and screech-owls often use the nest holes made by woodpeckers.
Nest-building is a demanding activity for birds. The nest must provide concealment, insulation, and shelter from predators and the weather. Some birds spend hours each day for many days at a time building their nests, while others simply lay their eggs on rock ledges or in shallow depressions on the ground. Others, such as swallows and swifts, use holes in trees or riverbanks, or build mud nests on cliffs or man-made structures such as buildings and bridges. Peregrine falcons, which mate for life and return to the same nesting site year after year, nest on several bridges in New York City, including the Verrazano Narrows Bridge and the Gil Hodges Memorial Bridge.
The American Robin, a common sight in New York City playing fields and parks, builds its nests in trees out of mud and grass. Both the male and female work together to build the nest, but only the female sits on the nest to incubate the eggs. The egg shells are such a beautiful color that it has its own name, “Robin’s-egg blue,” even though many other kinds of birds also lay blue or bluish eggs. Newly hatched robins and most other songbirds are featherless and helpless at birth; the scientific term for this is altricial. The parents must feed them until they are fully fledged (feathered) and ready to leave the nest. The hatchlings of many ground-nesting birds, waterfowl, and shorebirds, such as chickens, sandpipers, and ducks, are precocial, which means they are already covered in down and ready to move and feed on their own as soon as they hatch.
Many species of birds produce more than one brood of offspring in a year, in fact, the city’s familiar pigeons often produce four or five broods. Birds that are vulnerable to predators, such as quail, typically produce large broods of chicks, while those higher in the food chain, such as hawks and owls, may hatch only two or three chicks per season. Many birds build new nests each nesting season, while others, such as ospreys and bald eagles, use the same nest year after year, building it up over time.
Birds’ nests in New York City have become controversial and even developed fan followings. The Upper East Side’s famous red-tailed hawk, Pale Male, can be seen in his nest on an upscale apartment building in this trailer for a documentary movie about him. Another red-tailed hawk that nested at NYU was followed by the New York Times’ “City Room” blog. If you’ve been lucky enough to find a nest, don’t disturb it! You can help scientists by contributing your observations to the Cornell Laboratory of Ornithology’s NestWatch.
