The chimney swift is one of four regularly occurring species of swifts found in North America, the most common one found east of the Rockies. They have become accustomed to building their nests in chimneys as well as abandoned buildings and occasionally stone wells.

Adult chimney swifts are most commonly seen in flight, and usually in groups. When soaring, their long, scythe-shaped wings span about 12 1/2 inches, supporting a proportionately short body with a squared-off tail. The flickering, bat-like flight when flapping is due to short, massive wing bones. During this spectacular aerial ballet, swifts are most often patrolling the skies for mosquitos and the other small flying insects that constitute the majority of their diet. A sharp chippering or ticking call accompanies the swifts' flight.

At rest, an average 5-inch, 8-ounce adult is sooty gray to black with the throat slightly lighter or even silvery gray, in color. The sexes are identical in appearance. Both the claws and tail bristles are used to cling to rough vertical surfaces. Swifts are unable to perch or stand upright in passerine fashion.

Chimney swifts winter in the Amazon Basin of Peru. They arrive in the continental United States in late March and are gone by early November. Nesting begins in May and can continue into August. Chimney swifts are usually single-brooded. The female normally lays three to five white eggs in a nest of twigs broken from the tips of tree branches, glued together with saliva and attached to inside wall of a chimney. Both sexes are involved in nest construction and alternate incubating the eggs for 18 to 19 days, when the young begin to hatch. Their parents catch flying insects on the wing to feed them until the birds fledge from the chimney about 30 days after hatching.

The hatchlings are pink, altricial and completely naked at birth. They have sharp claws, which enable them to cling to textured surfaces, Within a few days, black pinfeathers begin to appear. The young are able to climb, and they exhibit preening behavior even before their feathers emerge.

By the time they are 8 or 10 days old, the babies' feathers begin to unfurl. By 15 to 17 days of age, their eyes begin to open. Soon, most of the flight and body feathers will be unfurled, but the feathers around the face and head will stay in sheath for several days, giving then birds a frosty-faced appearance.

By the time chimney swifts are 21 days old, they will cling tightly to the nest or chimney wall, rear back, and flap their wings furiously until they are panting and out of breath. Twenty-eight to 30 days after hatching, young swifts will leave the safety of their chimney for their first flight.

Once an entire brood has fledged, they will fly with their parents in slow, noisy parades around the area of the nest site. The young will return frequently to the roost during the first few days, but will soon begin to visit other roosts in the area.

At the end of the breeding season, the swifts' communal instincts peak prior to fall migration. They congregate in flocks of hundreds and even thousands at suitable roost sites.

Although chimney swifts can withstand a few early cool snaps, they will usually ride south on the first major cloud front that blows through the fall.

Read the Migratory Bird Treaty