The curious lives of Chimney Swifts
Its already past sunset so the light is getting dim. Curious little, twittering birds are whirling around in high-G force turns. On some unknown cue, the black creatures fall like a funnel into the chimney, not to be seen again until dawn. It must be a relief of sorts to finally rest. The Chimney Swift (Chaetura pelagica) spends its entire day in flight.
Unlike most other birds, swifts are incapable of standing or perching and must cling to a vertical surface when at rest. It does this with tiny feet tipped with short, sharp claws and a stiff, bristly tail. Flying, however, is the life of this bird. Feeding, bathing, drinking, copulating, even gathering tiny twigs for nests, are all done while airborne.
In flight, this bird has been described (aptly so) as a flying cigar. This sooty, gray to black bird, is about five inches long with a wingspan that can reach about a foot. They resemble swallows but can be told from them by their much shorter tail and their thin wings. In fact, they probably look more like bats than any other bird when flying.
There are four species of swift in the US; the Chimney Swift being the only one here in North Dakota. Swifts are all known for their speed and are indeed among the worlds fastest fliers. Watching them, one quickly gains an appreciation for this bird. They use stiff, fluttery wing beats to carve large sweeping arcs across the sky, sometimes very high. Not as maneuverable as swallows, swifts nonetheless spend their days in the air. Because of this habit, a tremendous energy requirement must be met. One source claims the swift diet totals about 25,000 flying insects per day, an impressive total.
This is yet another example of a species that has likely benefited from the settlement of humans. As recently as the 1940s, these birds were rarely found east of the Mississippi River. Now they are fairly common right up to the foot of the Rockies. Historically these birds roosted and nested in large dead trees or on cliffs. Now they are regularly seen in virtually any town using the chimneys of older buildings for such sites.
The nest of the Chimney Swift is a cup-shaped bracket made of fine twigs that is stuck together--and to the wall--with swift spit. Their glue-like saliva keeps the nest firmly attached to the inside of trees, cliffs or--more commonly now--chimneys.
I was surprised to learn that no matter how many birds a person sees disappearing into a chimney at the close of a day, there will only be one nest inside. At least in smaller chimneys. Apparently nesting adults tolerate other roosting birds but not other nesters.
Another mystery surrounding this bird was solved 60 years ago; that of their wintering grounds. Experts knew the birds left North America fairly early in the fall. But where did they go? Not until 1944, when banded birds were captured by natives, did we know that Chimney Swifts winter in the Amazon Basin of Peru.
But from early May until the first cold snap of fall the Chimney Swift will be around to entertain us with aerial acrobatics and a rapid, high-pitched, twittering, voice. Look above local parks and rivers to watch these birds feeding. To witness the nightly descent into a chimney, try South Elementary School in West Fargo.