Local Wildlife: Dance of the Chimney Swifts

A summer’s end spectacle as fleeting as it is enchanting

As September unfolds in Philadelphia, our days begin to shorten, and the golden light of late summer softens the edges of our cityscape. The seasons are changing. The warmth of summer still lingers in the air, but with a cool whisper of autumn as the sun sets. If you look up at dusk, you might witness the remarkable choreography of the Chimney Swift, a bat-like migratory bird passing through on its way to the Amazon River Basin.

Chimney swifts are small, dark birds with slender bodies — if you spot one, you might think it looks like a flying cigar with wings. They’re always on the move, darting and twirling through the sky in search of insects. For nearly all their lives, they remain aloft:  looping, swooping, making sudden turns and stops that seem to defy physics. They drink by skimming the surface of water mid-flight, and they bathe by gliding through rain showers. These tiny aerial performers are rarely still, except when they come together in a magical evening ritual.

In the fading light of day, if you’re near an old brick chimney or a tall structure, you might see them gathering in numbers that seem to multiply by the minute. They circle and swirl, forming a living cloud in the sky, their wings cutting through the air with soft, swift strokes. As more and more swifts join the gathering, the cloud takes on a life of its own, spinning faster and tighter, transforming into a delicate funnel that draws downward as if nature herself is pulling them toward the earth. Then in an instant, they vanish into their roost for the night – like they’re getting sucked into a vacuum.

This show happens every evening from late summer through October, a temporary and spectacular engagement. For a short time, our city is host to an impressive feat of nature, a display of breathtaking coordination that bridges the end of summer with the promise of change.

These chimney swifts are on a long journey, traveling along the Atlantic Flyway, a vast migratory route that stretches from their breeding grounds of North America to where they winter in South America. They pass through Philadelphia twice a year, once in spring as they head north to nest and then again in the fall, on their way to the warmth of the Amazon. They have been making this incredible journey for thousands of years, long before our city was built.

Standing in for hollow trees, Philadelphia’s chimneys and old towers now provide key shelter for local populations to gather before they all fly off together. For a few weeks, they’ll grace our skies with their thrilling nightly convergences. And then, as quickly as they came, they’re gone, continuing their southward flight, only to return again with the call of spring. This yearly encounter, though brief, is profound.

While we go about our daily routines, these tiny travelers remind us of the rhythms of the natural world that pulse through our own lives. As the seasons change, so too do we — moving forward, coming back, sometimes pausing to rest, and then taking off once more. The chimney swifts’ swirling dance above us is more than just a natural marvel; it is a reminder of our connection to something larger, a timeless cycle that repeats, year after year.

As we drink in these early autumn sunsets, here’s to taking a moment to enjoy the chimney swifts’ magical, miraculous aerobatics above us. Feel the chill in the air, the hint of autumn’s approach, and know that, for a short while, we share special space with these intrepid little birds. Here they are — just passing through — on a journey that spans continents, yet brings them right to our backyard, reminding us that we are all part of the dance.

🪽 TEN FUN FACTS ABOUT CHIMNEY SWIFTS 🪽

1. Chimney swifts are voracious insectivores, consuming up to one-third of their body weight a day.
2. A group of chimney swifts is called a “scream.”
3. Chimney swifts can sleep while flying if they need to.
4. Chimney swifts are some of the fastest flyers in the avian world with speeds of 30 – 60 mph.
5. A chimney swifts can fly 500+ miles per day – by the time it’s a year old, it will have flown as many miles as it takes to circle the globe.
6. Chimney swifts don’t sing, but instead communicate with high-pitched chip and chatter sounds.
7. Chimney swifts have sticky saliva that works like glue to clump twigs into tiny, c-shaped nests.
8. Both parents share the duties of hatching eggs and feeding their young by regurgitating insects.
9. If chimney swifts are flying low, rain is coming (the birds follow flying insects driven down by falling atmospheric pressure).
10. Some shamans say that dreaming of chimney swifts is a good omen, as long as they are flying. If you dream of nested swifts, that means someone in your life needs help.

WHERE TO WATCH CHIMNEY SWIFTS ROOST:

Mifflin Elementary clock tower (3625 Conrad Street, East Falls)
Dobson School chimney (4667 Umbria Street, Manayunk)
J.S. Jenks Middle School (8301 Germantown ave, Chestnut Hill)
Henry H. Houston School (7300 Rural Lane, Mt Airy)
The Discovery Center (3401 Reservoir Drive, E. Farimount Park)
Historic Fairmount Water Works (640 Waterworks Dr, Fairmount)
Old Germantown Friends Meeting House (47 Coulter Street, Germantown)
Awbury Arboretum  (1 Awbury Road, Germantown)
Society Hill (various)
Philadelphia Navy Yard (various)

Check iNaturalist.org and with local birding groups like Delaware Valley Ornithological Club and the Philadelphia Audubon Society. For great local bird walks and events, visit BirdPhilly.com.

About Murmurations

As you marvel at the swirling “birdnados” of chimney swifts this time of year, keep an eye out for another spectacular sight: murmurations of starlings. A murmuration is a breathtaking phenomenon where hundreds or even thousands of European Starlings fly together in a synchronized, flowing mass, creating stunning patterns in the sky. These undulating flocks move as if they are a single living organism, shifting direction in perfect unison without colliding. Scientists believe starlings murmurate to confuse predators, stay warm, and share information about good feeding grounds. Like the chimney swifts, starlings are also on a journey this season, gathering in larger flocks to prepare for migration or to find favorable winter habitats.

We hope you have enjoyed this month’s Local Wildlife Feature. Thoughts? Questions? Please leave in the Comments below. Check out last month’s spotlight on a prehistoric wonder in the Delaware River.