Laura Erickson's For the Birds

(Recording of a Chimney Swift)

A couple of weeks ago I received a letter from a woman who lives across the street from the school in Togo, Minnesota–she’s been observing huge flocks of Chimney Swifts flying into the school’s chimney every evening at dusk. She wonders what time the birds leave the chimney in the morning, where they go all day, and whether they build their nests in the chimney.

Chimney Swifts are one of the few native American birds that have benefited from settlement here by Europeans. Before the white man came, these little “flying cigars” spent their summers in hollowed out standing trees with openings in the top—this unique habitat requirement was hard to find even in the forest primeval, and swift numbers were correspondingly low. But with white settlements, the swifts quickly discovered that chimneys give them everything they need and more—now they can also get warmed up on cold mornings, taking advantage of the heat from furnaces and fireplaces. Although chimneys do present dangers from fire, toxic gases, and even suffocation when soot is dislodged, overall the benefits far outweigh the hazards, and the swifts have increased and multiplied.

Every spring, as soon as flying insects are abundant, flocks of Chimney Swifts return to their chimneys in the eastern United States and Canada. These are the most airborne of all Northland birds–they never touch the ground in their whole lives if they can possibly help it, spending their days in flight and their nights clinging to their vertical homes. They are uniquely adapted for this lifestyle, with specialized short, massive wing bones giving them their stiff, jerky flight; and tail feathers with stiff central spines to support them on their roosts. Swifts belong to the family Apodidae, which means “without feet.” In truth the name isn’t quite correct, but the legs and feet of swifts are too tiny and weak for walking or standing. If one accidentally ends up on the ground, it cannot take off again. They do have long, sharp claws and a completely reversible hallux, to aid in clinging to wood or brick.

Chimney swifts sleep in chimneys or hollow trees. They generally wake up at first light, but on cold mornings when insects aren’t available they often sleep in. Once they leave the chimney in the morning they spend their entire day in flight, spreading out over the countryside in search of flying insects. Like Whip-poor-wills and Nighthawks, swifts have a tiny beak, but a mouth which opens incredibly wide—their gape extends all the way under their eyes.

Chimney Swifts build their nests out of twigs that they break off of trees with their feet. The half-saucer-shaped nest is held together by glutinous saliva, which hardens and fixes the twigs to the chimney so securely that even hard summer rains seldom dislodge nests. This unique swift spit is edible–the nests of a related Asian species of swift are the source of “birds’ nest soup.”

Our little Chimney Swift flies to South America each fall, before flying insects become scarce up here. It winters in western Peru and the Amazon Basin of eastern Peru, northern Chile, and northwestern Brazil. Although the bird nests only in North America, never on its wintering grounds, it still needs adequate habitat on its tropical sojourn. Chopping Brazilian trees to build lake walks in Duluth makes it harder for swifts to find shelter down there.

(Recording of a Chimney Swift)

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