My memories of the evening skies over my home town in Pennsylvania in August are of dozens of chimney swifts, darting and diving for insects, while the twitter of their high, hard chips run together. Common summer residents in the eastern half of the continent, chimney swifts are the best known and most often seen of the four Northern American swifts.
Dubbed “cigars with wings,” these small, black, short-tailed, long-winged, fast fliers favor cities because they use chimneys in which to roost and to build their nests. Some large factory chimneys house hundreds of swifts. In some cities where they roost in masses, the birds assemble in a funnellike formation above the building just before dark. Then, as the flock moves in spiral flight, birds at the tip of the funnel drop rapidly into the opening and quickly the funnel disappears into the chimney where the birds cling to the walls for the night. Before there were chimneys, the swifts used tree cavities with vertical entrances like chimneys.
Perhaps the most interesting part of these most interesting birds is their nest. Built entirely of twigs, it is literally glued to the sides of chimneys with the birds’ glutinous saliva, which hardens when exposed to air (birds’ nest soup is made from oriental swift nests made entirely of their saliva). Four to five white eggs hatch in 18 to 21 days, but the young remain in the chimney nest for another 30 days until they grow feathers to fly out.
George H. Harrison