If you hear something that sounds like gremlins chattering in your old brick chimney this July, don’t panic — you probably just have baby chimney swifts.
After a long day spent snapping up insects and flying through the summer sky, chimney swifts return home, helicoptering down brick chimneys to chicks waiting in a teacup-sized nest of twigs glued together with spit.
Watching these aerial acrobatics is “a special treat,” according to Stanley Temple, an emeritus professor of conservation at the University of Wisconsin-Madison.
This treat, however, is growing less and less common in Wisconsin’s towns and cities. Chimney swift populations have been declining since the early 20th century.
“If you do the math,” Temple said, “there are going to be half as many chimney swifts in about 25 years or 20 years as there are today. To lose half the chimney swifts in a person’s lifetime is significant.”
Efforts to halt this decline largely fall on an unusual conservation strategy: maintaining a disappearing piece of human architecture — brick chimneys.
In June, the state Department of Natural Resources and the Wisconsin Chimney Swift Working Group launched a survey to determine if building owners have chimney swifts living in their chimneys or other similar structures.
Once the groups learn where chimney swifts are nesting and roosting throughout the state, they plan to help building owners repair dilapidated chimneys that would otherwise be demolished.
“Chimney swifts nest one pair to a chimney, and they go back to the same chimney every year,” said Sandra Schwab, who chairs the Wisconsin Chimney Swift Working Group. “So if that chimney is capped or it’s demolished, their habitat is seriously diminished.”
Unlike eastern bluebirds, whose rebound in Wisconsin is likely due to the construction of bluebird houses, artificial homes don’t seem to be the answer for Wisconsin’s chimney swifts.
Chimney swift “towers” are chimney-like structures built from wood slats and have been successfully used as chimney swift nesting sites in southern states.
But Wisconsin’s swifts are pickier. Schwab knows of only one example where chimney swifts moved into these towers, and that was only when the tower was built on the footprint of a demolished brick chimney that previously hosted swifts.
Maintaining existing structures that are used by swifts is a key goal of the Wisconsin Chimney Swift Working Group.
Are chimneys enough?
But solving this housing crisis may not help the chimney swift rebound like the eastern bluebird.
During recent fieldwork studies, William Mueller drove down National Avenue in West Allis, stopped at regular intervals, and listened and watched for chimney swifts. He also noted the number of chimneys he saw along this route.
Mueller, who previously directed the Western Great Lakes Bird and Bat Observatory, saw that though chimney swifts live in the area, not all the available chimneys were occupied.
“Are chimneys being capped as big an issue as we think?” Mueller asked. “Possibly not.”
Chimney swifts are a class of bird called aerial insectivore — that is, they only eat flying insects. Birds of this type, including whip-poor-wills and sparrows, are disappearing.
Though the cause hasn’t been pinned down,
recent studies suggest that the number of insects across the world is falling precipitously. Cleaner car windshields are probably the only positive outcome of this decline, which puts just about every food chain on the planet at risk — including that of the chimney swift.
Not only is the swifts’ food source disappearing, they are also contending with extreme weather.
Chimney swifts migrate each winter to South America, crossing the Gulf of Mexico. These little birds are no match for hurricane gales, and the increased number and intensity of tropical storms and hurricanes could be killing many of them during these migrations.
Even Wisconsin’s changing weather could be a culprit. Heavy rainfalls, which have become more frequent in the state, can dislodge chimney swift nests, dropping the babies into fireplace hearths or the bottom of a silo.
Faced with all these factors, a “simple, direct solution” is probably not possible for reviving chimney swift populations, Temple said.
“But for heaven’s sake, if you have chimney swifts nesting in your chimney, accommodate them for a few weeks!”
I’ve got gremlins in my chimney
Not all building owners are keen on hosting wild tenants.
When chimney swifts were discovered in a fireplace in UW-Madison’s Agricultural Engineering Building last year, Anna Pidgeon recalls working with the campus physical plant staff to leave the nest alone.
“They felt very negatively about encouraging any kind of wildlife to live in chimneys,” said Pidgeon, a professor of avian ecology at UW-Madison. “That feeling of animals as negative things in our environment is a big one to overcome.”
The Wisconsin Chimney Swift Working Group uses its platform to educate the public about chimney swifts and overcome misconceptions.
The group emphasizes that chimney swifts aren’t a danger to people or buildings. The spittle-bound nests fall apart each winter, so chimneys that host swifts don’t get filled up with old, flammable nests.
They also work with chimney sweeps across the state to delay cleaning out chimneys with nesting pairs until after the birds have left the nest.
Though the characteristic chirps of baby swifts can be annoying, they leave the nest soon after the sound become noticeable.
“All they need from us is a little awareness and tolerance,” Schwab said.
Jordan Nutting is a mass media fellow with the American Association for the Advancement of Science writing about science at the Journal Sentinel this summer. She’s working on a doctorate in organic chemistry at the University of Wisconsin-Madison.