Their twittering call is often heard before the bird is seen circling, gliding and sweeping overhead above our cities and countrysides. They are the chimney swifts.

Swifts are among the fastest and most aerial of all birds, courting, feeding, drinking and bathing on the wing, and each year are seen fluttering down Minnesota chimneys after wintering in South America. The blackish chimney swifts have 5-inch-long bodies with long curved wings, each longer than their bodies. For years naturalists like me have described them as flying cigars. They feed exclusively on insects caught in the air and fly continuously all day, sometimes covering about 500 miles a day.

Chimney swift nesting takes place in May through July, in chimneys, airshafts, silos, open wells and hollow trees. Now that nesting is done, and insects soon will be difficult to find, these swifts are staging for migration by using communal chimney roosts. Years ago, close to this calendar date, I stood by an elementary school in Prairie Farm, Wis., at sunset looking up toward the school’s chimney with our young son Andrew. About 130 chimney swifts were gathered, all flying in the same direction around and around the chimney. We watched the first two swifts drop into the chimney eight minutes after sunset. The rest followed in a thin stream with most of them going in 18 to 21 minutes after sunset. We counted 129 birds that had dropped in by 23 minutes after sunset. Finally, one lone swift entered the chimney 32 minutes after sunset. Soon it was quiet.


Jim Gilbert’s Nature Notes are heard on WCCO Radio at 7:15 a.m. Sundays.