Recently a group of swift fans gathered outside of a Pittsburgh restaurant in anticipation. But these “swifties” aren’t here for a pop concert or a celebrity sighting. They’re gathered together along a side street to witness a natural phenomenon that happens around dusk this time of year. It’s the roosting of chimney swifts.

LISTEN: “Chimney Swifts Put on a Show Before Fall Migration”

Sarah Koenig is conservation director for Audubon Society of Western Pennsylvania, and she directs people to look up at the chimneys at the rear of the Church Brew Works. It’s an old church that’s been converted into a restaurant and brewery.

It’s noisy, with nearby traffic, the restaurant’s exhaust fan, kids practicing football on an adjacent field. But fifty people have their eyes peeled for the little cigar-shaped birds that are just starting to arrive.

“I love just kind of seeing them come out of nowhere to join the group,” Koenig says.

Chimney swift up close. Ed Schipul/flickr

Chimney swifts spend their summers in eastern North America breeding, and their winters in the upper Amazon. Koenig says they’re regrouping now to migrate south. When they’re here, chimney swifts perform an important service.

“They’re like the ultimate urban insectivore. They eat 3,000 to 5,000 insects per day,” she says. “So they eat mosquitoes, and other biting things that might annoy us.”

Koenig says the little, gray birds spend the whole day on the wing, cruising around for insects and even mating in the air. They belong to the same order as hummingbirds, and they’re tiny, short feet can’t perch on a horizontal surface. The swifts have to cling to rough, vertical surfaces, like the inside of a chimney. But it has to be the right kind of chimney.

“It’s got to have something that they can grab hold of,” says Joan Schoff, one of the many experienced birders in the crowd. “Now there’s a lot of chimneys that have steel or aluminum flues. Most of us either have a cap on our chimney, or we have the wrong kind of chimney.”

Schoff says she’s never seen swifts go down into a chimney to sleep for the night.  

“Something like this makes me feel small. Just kind of in awe of bigger things than me.”

In rural areas, chimney swifts roost in hollowed out trees, but development has pushed them to adapt in the city and suburbs. Now they’re common in communities with old, brick chimneys. But they’re “near threatened,” says Sarah Koenig, as pesticides reduce their food sources, and new development means chimneys are becoming a thing of the past. She says chimney swifts have lost 50 percent of their population over the last 50 years. Audubon and partners have built smaller, stand-alone chimney swift towers to help increase their habitat.

Like smoke going down a chimney

Dozens of birds swirl around the chimney as the sky darkens; it’s a dramatic sight against the clouds threatening rain. You can hear them chittering, and the birds move fast. As they form into a group, people stop using their binoculars, because the individual birds are too hard to keep in their sights. The street lights are on, too, and everyone is shielding their eyes.

“Once a few drop in, they’ll all go down,” says Koenig.

WATCH: Chimney Swifts near Church Brew Works

(credit: Audubon Society of Western Pennsylvania and Lauren Nagoda)

“It’s like watching smoke go back down a chimney. It’s amazing,” says Rob Protz.  

Protz is an experienced birder who monitors peregrine falcons. He’s seen this spectacle before, but he’s just as excited as everyone else.

“There they go!” Protz exclaims, and the crowd echoes his words.

Eric Blondin is new to all of this. He says he just started dating a serious birder.

“I couldn’t find my keys the other day. And then I’m sitting here, and these birds migrate thousands of miles to the same chimney. And I couldn’t find my keys,” he says. “Something like this makes me feel small. Just kind of in awe of bigger things than me.”

The birds will leave the chimney in the morning. Audubon estimates about 200 swifts roosted at the Church Brew Works that evening. More may come to join the roost before they finally leave the area in October to migrate south.

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If you’d like to see the chimney swift show yourself, there’s an interactive map to help you HERE.

And if you spot some, you can report it at the Audubon Society’s Chimney Swift Activity Report

Photo(top): Steve Schroeder/flickr