Laura Erickson's For the Birds

Retaped in 1987. (Recording of a Chimney Swifts).

That chittering sound is made by Chimney Swifts–little brown birds that fly on stiff, arched wings and resemble flying cigars. They nest in hollow trees and chimneys, but don’t call them chimney sweeps, unless you actually see one wearing a tophat and carrying a broom.

In spite of their drab coloring, chimney swifts are most closely related to hummingbirds. Both belong to an order of birds called “Apodiformes,” which means “without feet.” Although both swifts and hummingbirds do have feet, they are very reduced in size. If a swift lands on the ground, it may even have trouble taking off again because its tiny feet are so useless. It has long claws on its tiny toes, though, and hard, sharp spines at the end of its tail, which help it to cling to brick or wood.

Swifts may not be much on their feet, but on the wing they are without equal. All of their food gathering, courting, drinking, bathing, and gathering of nesting materials take place in the air, and they sometimes even mate on the wing–sort of like Arthur Dent for you Douglas Adams fans. Ornithologists estimate that one banded Chimney Swift flew 1,350,000 miles during its nine-year lifespan.

The flight of swifts is fascinating. Their jerky, flickering motion is unique in the bird world, thanks to their short, massive wing bones, completely different from the long, slender wings bones of swallows. People used to believe that swifts beat their wings alternatively. It took slow motion photography to prove that they can’t–but when a swift wheels and turns in the air, it does sometimes beat one wing more strongly than the other.

Chimney Swifts are gregarious. Hundreds, or even thousands, can live together in a single chimney or silo. Like the nighthawk, they are among the few birds which have increased their populations thanks to civilization. Their pleasant, friendly-sounding chittering is a welcome sound in a big city, and the fact that they each eat thousands of mosquitoes is an added bonus.

Ornithologists have a hard time studying chimney swifts–they’re either darting about the skies, in and out of view, or hiding in their roosts, usually in hollowed out tree stumps or in chimneys, too small for human access. And it’s impossible to keep track of individual birds unless scientists dye their feathers–Males and females look alike, and as soon as young birds fledge they look just like their parents. The nest is built from twigs gathered on the wing, cemented together with swift spit. The saliva of these birds is unique–a thick, viscid glue, which is actually edible. Some Oriental swifts make their entire nests of this material, which is the source of “birds’ nest soup.” But don’t try to eat the nest of a chimney swift–the spit may be edible, but the sticks aren’t.

(Recording of a Chimeny Swift)

This is Laura Erickson, and this program has been “For the Birds.”