By Marty Corfman
[from fall 2026 newsletter]
On Monday, August 24th, I had the pleasure of leading a Chimney Swift Watch at Wartburg Theological Seminary. I decided to publicize the event to the full community through all our available media outlets, and I was so pleased to meet so many new faces as a result! This is the second time we’ve held this outing, and it’s been such a success that I plan to make it an annual event. About 36 people of all ages attended this year—many of whom had no experience with birding, let alone knowledge about Chimney Swifts!
I did my best to answer questions about the fascinating roosting behavior of these wonderful birds. It is incredible to see them congregate in the sky, flying randomly all over the area while catching bugs for a bedtime snack. Eventually, they form a dynamic vortex, swirling in a funnel formation like a single organism. Then, one bird at a time—and soon dozens at once—they stall over the chimney, fold their wings, and drop tail-first into the opening to roost for the night.
Once inside, they cling vertically to the inner walls, filling the chimney from the bottom up as more birds arrive. They roost tightly together in dense clusters for warmth. We had a moderate number of birds this year; hopefully, the larger migrating flocks will arrive over the next couple of weeks as they head south.
Chimney Swifts rely on unlined chimneys and hollow trees for roosting and nesting sites. As old chimneys are decommissioned, capped, or torn down, and dead trees are removed, these vulnerable birds face severe population declines across North America. In fact, they are officially classified as Threatened in Canada. Widespread pesticide use has further compounded the problem by drastically reducing the flying insect populations they depend on for food.
These incredible aerialists spend virtually their entire lives in flight, landing only to incubate eggs or roost at night. Because they rely on daylight to navigate, they will not fly in the dark and can even be tricked by solar eclipses or severe storm clouds that darken the sky, prompting them to return to roost until the false “dusk” passes. However, they do not fly in all weather conditions—heavy downpours, fog, or prolonged cold spells ground them, as rain suppresses flying insects and impairs their flight.
One of my favorite facts about these birds is how they construct their nests. During the breeding season, specialized salivary glands produce a sticky, glue-like substance that they use to cement small twigs together and attach the nest to a vertical wall. They gather these twigs entirely on the wing, snatching dead twigs off branches with their feet as they fly past! While they roost communally in large numbers during migration, breeding pairs seek out individual sites during the nesting season, returning to communal roosts only after their young have fledged.
I hope you get to witness a Chimney Swift roost for yourself this season! Otherwise, please join me for next year’s watch!
