In the late summer and early fall, the late evening skies can sometimes host a marvelous show of thousands of birds swirling and twirling in unison. This show is performed by flocks of small birds called chimney swifts, and as their name implies, it most often is seen close to old tall chimneys. Right at dusk, as the sun is setting, thousands of chimney swifts will swirl near a chimney, and then suddenly, as if following some stage cue, spiral in what appears to be a choreographed funnel, as they descend into the chimney itself.
Chimney swifts are small quick birds that spend their summers in the northern hemisphere to breed. They are not very big birds, between the size of a sparrow and a robin, with a body that is about 5 inches long and wings that are about 11 inches long. They are dark grey-brown with skinny cigar or tube-shaped bodies, a light-colored throat and a round head. They have short tails and a very wide beak that help them to eat their prey (insects) in flight.
The most distinct part about a chimney swift is how tiny its feet and legs are. Unlike birds you often see around feeders, like cardinals or robins, chimney swifts’ feet and legs are so small they cannot actually sit or perch on branches, but rather they cling tightly to bark or brick walls. They spend most of their life flying!
Chimney swifts get part of their names because they are swift flyers, elegant and fast. The “chimney” part of their name comes from their behavior as they have often been found going into or coming out of old chimneys. Chimneys are where this species currently roosts, or groups together to sleep overnight. Before European settlers came to America and before chimneys were found on the North American landscape, chimney swifts would use old hollowed out trees to roost inside of, or periodically they would roost inside caves. But chimneys quickly replaced both dead trees and caves, in part because old trees were removed, so chimney swifts quickly adapted to clinging to the inside of chimneys! Modern chimneys are not ideal for chimney swifts because they have narrow flues and are most often capped to prevent animals from entering a home, and yet there are still few old hollowed trees on the landscape, leaving chimney swifts with fewer and fewer places to nest.
We only really see chimney swifts here in North Carolina in the late summer as they prepare to leave for the winter. Where do they go? Chimney swifts are actually residents of South America, where they spend the majority of their life. In the springtime they migrate north, where they have fewer species to compete with for food and home during the breeding season. Once paired up, a set of two chimney swifts will nest inside of one chimney, very rarely sharing a chimney with another pair of swifts. Swifts build their nests using special saliva to essentially glue some woven twigs together and adhere them to the wall of the chimney. Baby swifts are too big for the small nest by the time they are two weeks old, and although their eyes are yet to open and they still cannot fly, they leave the nest and begin to cling to the wall of the chimney, just like their parents.
After young swifts have fledged, and no more nesting is occurring, chimney swift behavior begins to change. As swifts begin their migration south, they become communal. Occurring in the late summer, roosting is when many swifts will congregate into one chimney each night. Roosts can home hundreds of swifts and provides warmth for the birds in the cooler late summer nights. Chimneys that may have been home to a pair of breeding swifts, and their offspring, now becomes a home to hundreds.
Roosting is likely the most notorious of chimney swift behavior and is certainly the most conspicuous. As dusk approaches each night, chimney swifts will begin to fly in large flocks, in a mostly circular fashion. A remarkable large circle of quickly-flapping birds, near an old chimney, is often hard to miss. Suddenly, without an obvious (to humans) sign, the chimney swifts will begin to quickly funnel into the roost, a small tornado of feathers and chirps. Within about 10 minutes, all the birds will have accommodated themselves inside the chimney, ready to sleep for the night. Chimneys that have roosting swifts will continue to accommodate this spectacle for a couple of weeks in September, before some unknown driver urges the birds to fly south for the winter.
Here in Raleigh, there are a few old chimneys left, and even one new chimney-like tower built just for these birds. The Walnut Creek Wetland Park hosts an annual Chimney Swift walk, to observe the large gatherings of swifts that enter the old chimney at Carnage Middle School. Oberlin (formerly Daniels) Middle School also has an old chimney used by the swifts, a feature the school chose to keep just for the birds even when the rest of the school was being updated for modern heating and air. Other hot spots include a couple of chimneys in downtown Raleigh, near the old News and Observer building (look for them from a bench at Nash Square) and one near the Transfer Co. Food Hall (can be viewed from Moore Square). The North Carolina Museum of Natural Sciences even built a chimney swift tower at their Prairie Ridge Ecostation, just for the Chimney Swifts to have a safe place to nest and roost, as fewer and fewer old chimneys, old trees, and small caves are available to the species. As the days get shorter the swifts are quickly moving south; see if you can find some in the skies one night soon, and mark your calendars for their nightly show next September!