By Tom Dennis
Chimney Swift, Chaetura pelagica
A common summer bird in Michigan is the Chimney Swift and like the Tree Swallow it’s a swift flyer and an even higher flying insect eating machine! This little creature was tagged by famous bird expert Roger Tory Peterson as a “flying cigar”; a perfect description. Chimney Swifts don’t sit still in the sight of people so just seeing one can be tricky if you don’t know what to look and listen for.
Chimney Swifts nest only on vertical surfaces and they benefit from mankind as buildings and chimneys have greatly increased their nesting sites which formerly were limited to hollow trees. They are a gregarious species and it’s common to see a dozen or more birds flying together. One of the largest colonies known to exist is in Farmington, Michigan in the large chimney of a winery where up to 50,000 individual birds have been known to roost and nest. The genus name Chaetura is a combination of two Ancient Greek words: chaite, meaning “spine” and oura meaning “tail”. The shafts on the tail feathers end in sharp points and are used to assist with stability while perching on vertical surfaces. The specific epithet pelagica refers to its nomadic lifestyle, after the Pelasgi tribe of ancient Greece.
There are 101 species of swifts worldwide but only six visit North America and the Chimney Swift is the only commonly occurring species in the eastern United States and Canada. They are long-distance migrators, spending winters in Central and South America.
Chimney Swifts don’t exhibit sexual dimorphism, although males are slightly larger than females. They have a brown upper body that shows a slight sheen, a gray head with dark brown eyes and a white throat. They weigh from 0.6 to 1.1 ounce distributed over a short body with a one-foot wing span. The feet of swifts are designed to cling to vertical surfaces and they are completely unable to walk or perch. The hind “claw” can be rotated forward to meet the front claws to increase grasping power. They fly constantly during waking hours and they do it well, even drinking and bathing by smacking the water with their bodies and lifting immediately to resume flight. The rapid and erratic flight often leads to them being mistakenly identified as bats. They have a general purpose bill with a very large gape, meaning it opens widely to catch insects and spiders. The song is a high pitched “chitter, chitter, chitter” and it’s a dead giveaway that they are overhead. I only look up for these amazing creatures when I hear the “chitter” as they can fly out of our range of sight; often over a mile high to forage.
Nest building is unique in that the birds break sticks off trees while in flight and glue them into a shallow oval bracket using large amounts of their saliva. Their diet is exclusively flying insects and airborne spiders. Both parents assume feeding responsibilities and researchers estimate that a pair of adults with three chicks consume the weight equivalent of 6,000 housefly-sized insects per day. That’s what I call an efficient exterminator!
The Chimney Swift population is estimated at 7.8 million birds and because many nesting sites (chimneys and old buildings) have been demolished and chimney designs have changed, their numbers have been significantly reduced from historic levels. Because of these declines, the Chimney Swift has a conservation rating of “near threatened”. Listen and look, these wonderful birds are city and country dwellers.
