It’s seldom that urban dwellers get to see more of a bird than people who live in more rural settings. That’s often the case for chimney swifts, though, eastern North America’s little “flying cigars.” These little known sooty dark gray birds are one of the species that have suffered the steepest declines in population since the 1960s. Like most other neotropical species (birds that winter in Central and South America), the cause is habitat loss. Habitat loss for chimney swifts is different from most other species, though. Their current habitat is primarily man-made.
Chimney swifts once lived in hollow trees, caves, and chimney-like fissures in cliff faces. They nested in areas east of the Mississippi River and in eastern Canada. Timber harvest removed many of the hollow trees as settlement moved westward, but the little birds adapted to new habitat that was created in the form of chimneys and rough-lumbered outbuildings. They cement their small loose twig nests to the inside of rough vertical walls with glue-like saliva. Heating fires weren’t needed during the nesting season, and cooking fires were often moved outdoors; leaving the chimneys available for nests. Coal soon became a dominant heating fuel and large diameter brick chimneys were (and still are) part of many older homes. Thanks to such chimneys, swift habitat expanded west to the Rocky Mountains and their numbers likely reached a peak during that time. As gas and oil replaced coal as a primary fuel, many of the old brick chimneys were capped or lined with more modern metal pipes that are unsuitable for swift nests. Newer heating systems that vent through the walls do away with chimneys altogether.
Swifts are fast fliers on stiff, curved wings that carry them on sunrise-to-sunset bug hunting flights high into the air above their urban homes. Their wings seem to flutter as they alternately flap and sail through the air. They frequently utter a twittering call as they bank and swoop to capture flying insects, their only food. Sometimes several birds will hold perfect formation as they maneuver through aerobatic displays that the Blue Angels would have difficulty trying to copy. They cannot perch on branches or wires like other birds. Their tiny feet allow them only to cling to rough vertical surfaces and are used to help them gather the few little twigs they need for a nest. These are snapped off of trees as they fly though the treetops, and carried back to the nest site in the bird’s short, but wide bills. They sometimes bathe on the wing, too, by splashing onto the surface of ponds or streams, bouncing back into the air, and shaking the water from their feathers as they fly.
Even though chimney swifts are often seen flying in groups, they are not colony nesters. A chimney, even a large one, will typically support only one nesting pair. Unmated and non-breeding birds may roost together in larger groups even in a nesting chimney, where their presence is tolerated by the nesting pair. Sometimes one or more non-breeders will assist the nesting pair in nest building and feeding the young. Sometimes dozens or even hundreds of swifts will funnel into a chimney as a night roost during migration. With only one nest per chimney, each remaining usable chimney is critical for the species’ survival.
A new trend is building chimney swift towers to replace disappearing old chimneys. It’s a major project, though, and requires more materials and skill than building a small truckload of bird houses for other birds. A recent Eagle Scout project built a swift tower just east of the campground at new Dakins Lake Park on the north side of Zearing. There’s information on line on how to build one or even to open up an unused old brick chimney. Old concrete or tile block silos also offer possible nest and roosting sites. Chimney swift numbers may never again reach what they were during the heyday of brick chimneys. Their future as a species is now dependent upon human planning and action to insure the continued availability of suitable nesting sites.
Steve Lekwa is a former director of Story County Conservation.