Chimney swifts are in a marked decline
OKAUCHEE - A storm had descended on Okauchee.
Not a thunderstorm or tornado such as moved through southern Wisconsin in previous days.
The weather on Wednesday evening, in fact, was mild, with a puff of northerly wind and peeks of blue sky.
This was another, much more welcome, force of nature.
As dusk gathered, a vortex of winged acrobats formed in the airspace above an old school.
The birds - chimney swifts - swooped and soared over the building in an aweinspiring display of aerial agility.
The show started about 40 minutes before sunset.
Four swifts soon became 10 and then 20. As the sun touched the trees, perhaps 200 churned the sky in a clockwise formation.
At times, one or a dozen birds broke from the pack and fluttered toward the school’s large chimney, then veered away. It was not yet time for bed, apparently.
The birds’ chattering calls echoed over the retired playground.
Five minutes after sunset, a signal seemingly had been sent: swifts began floating down and entering the brick chimney.
Dozens of birds followed, as if pulled in by a vacuum.
Meanwhile, new arrivals joined the flock in the sky. At its peak, perhaps 400 birds circled at once above the school.
By 45 minutes after sunset, the spectacle was over. An estimated 1,000 swifts had entered the chimney.
The behavior is part of what gives the species its name.
The birds commonly nest and roost in chimneys. The late-summer gathering in Okauchee was a flock preparing for migration.
To the delight of birders, the feathered extravaganza also was taking place at dozens of other sites in Wisconsin, many of them in urban settings.
The large number of swifts observed at individual roost sites, however, belies a troubling trend: it and similar species are in a marked decline.
Chimney swifts, common nighthawks, barn swallows, whip-poor-wills and purple martens all nest in Wisconsin and all are suffering drops in numbers, according to Bill Mueller, director of the Western Great Lakes Bird and Bat Observatory in Port Washington.
The birds belong to a group called “aerial insectivores.”
“These are some of our favorite species and well-known to most people since many of the birds nest and live in urban and suburban areas,” Mueller said. “It’s a great concern to see them in decline.”
Although still found across much of the globe, swifts are experiencing a 6% to 8% annual population decline, Mueller said.
To help study aerial insectivores, the WGLBBO is working this summer with 17 cooperators to monitor routes and count birds in Milwaukee and surrounding communities. The organization has information related to the class of birds published on its website.
A Facebook group is also dedicated to regional efforts to study and assist aerial insectivores. The plight of chimney swifts and similar birds is the focus of a September conference in Pewaukee.
The event, organized by the Wisconsin Bird Conservation Initiative and Bird City Wisconsin, is titled “S.O.S. for Our Flying Bug Eaters: Addressing Declines in Chimney Swifts, Nighthawks, Bats and other Aerial Insectivores.”
Mueller said swifts, nighthawks and the other similar species are not only beautiful to watch but they provide a service to humans by eating insects.
“We’ve got every reason to try to help these birds,” Mueller said.
Sometimes called a “flying cigar with wings,” chimney swifts are native to Wisconsin and likely originally utilized hollow trees and caves as nesting and roost sites but adapted well to the human-built environment.
Now most are thought to nest on the vertical surfaces inside chimneys.
The species is extraordinary in many regards.
Although it’s hard to believe, chimney swifts spend their entire lives in flight, including when they eat and drink, and only roost at night above in nests or chimneys above the ground — they never touch terra firma.
When it comes time to build their nests, the birds nip twigs from the crowns of trees, bring them into a chimney and, in a project that would impress any mason, fasten the sticks together with their own saliva.
This summer, Tom Schultz of Green Lake was able to observe and photograph a chimney swift nest in an abandoned building in Green Lake recently acquired by a conservancy.
The young birds returned to the nest for several days after fledging in early August, but then moved on, likely with their parents, to other roost sites in preparation for migration.
Like most birds, chimney swifts have three toes facing forward and one pointing backward. But the species is able to rotate its back toe to help it hold vertical walls.
And in a relatively rare behavior, family groups of chimney swifts, often including the previous year’s offspring, participate in feeding and rearing new hatchlings.
Everywhere they are found, the birds inspire awe. A small crowd of human onlookers gathered Wednesday night in Okauchee.
“Aren’t they amazing?” said Ed Hahn of Watertown, who had brought his grandson, 1-year-old Gabe Sorenson, to see the birds.
Tim Brass of Okauchee walked over to view the flock. He was accompanied by Whinnie, his standard poodle.
“This is my first time seeing this,” Brass said. “It’s hard to get your head around.”
As full darkness settled over the old school, the sky finally appeared still.
We could only guess how tightly the birds were packed inside the chimney.
The spectacle of chimney swifts roosting typically continues into early September at southern Wisconsin sites.
A Sunday night viewing, led by Bird City Wisconsin, is scheduled in Whitefish Bay.
If you haven’t seen this wonder of nature, don’t wait. And consider erecting a roost tower or other projects in your community to improve the future for these beneficial, native species.
The Wisconsin sky wouldn’t be the same without them.