Before European settlement brought chimneys to North America, Chimney Swifts nested in caves, cliff faces, and hollow trees. Their numbers rose accordingly, but a recent shift in chimney designs toward covered, narrow flues are unsuitable for nesting and may be contributing to a decline in this species’ numbers.
Chimney Swifts are among the most aerial of birds, flying almost constantly except when roosting overnight and nesting. When they do come to rest, they never sit on perches like most birds. Their long claws are suited only for clinging to the walls of chimneys and other vertical surfaces.
Swifts even bathe in flight: they glide down to the water, smack the surface with their bodies, and then bounce up and shake the water from their plumage as they fly away. Large numbers of Chimney Swifts roost together in a single chimney during the nonbreeding season. There’s warmth in numbers: during cold nights, the temperature inside a chimney roost can be 70°F warmer than outside.
Unmated swifts continue roosting together in the summer, sometimes in large groups. But the species does not nest colonially: you’ll find only one breeding pair nesting in any one chimney. The pair may tolerate other nonbreeders roosting in their chimney.
The Chimney Swift uses glue-like saliva from a gland under its tongue to cement its nest to the chimney wall or rock face. Sometimes an unmated swift helps the breeding pair rear the young. The young outgrow the nest after about two weeks and have to cling to the nearby wall, in many cases even before their eyes are open.
The oldest recorded Chimney Swift was a male, and at least 14 years old when he was recaptured and released during banding operations in Ohio in 1970. He was banded in the same state in 1957.
