Wednesday, September 9, 2015

The Race Is to the Swifts

In February and March, people visit San Juan Capistrano in hope of seeing the return of cliff swallows to their nests beneath the eaves of old mission buildings. March is also when folks await the return of buzzards (turkey vultures) to Hinckley, Ohio.

And every summer night, hundreds of people gather to watch more than a million Mexican free-tailed bats pour out from under a bridge in Austin, Texas.

But if you've missed these annual animal aggregations, never fear. Because now is when Vaux's swifts are streaming south for the winter, pausing to rest and feed in the vicinity of Monroe, Washington--and when people flock to an old chimney to watch the little birds plunge into it at night.

Vaux's swifts, often described as "flying cigars," are North America's smallest swifts at barely 4.5 inches in length. They spend spring and summer in western North America, primarily in coastal states and Mexico, ranging as far north as southern Alaska . Then they skip out on us to spend winter in warm, sunny central America. Clever birds.

"Wait a sec," says you. "What was that bit about the chimney?"

Yes, it's true, Santa isn't the only organism that plummets down chimneys on a predictable schedule. Vaux's swifts nest in cavities, in hollow trees, and chimneys. During migration, they cram into trees and chimneys by the hundreds and thousands in order to keep warm--and safe from predators--at night.

Photo from Washington Dept. of Wildlife
They cling to vertical surfaces with sharp-clawed toes. Their short legs and feet are completely unsuitable for walking on the ground and not much use for perching, either.

When they're not stuck upright as if held in place by Velcro, they're flying. Vaux's swifts do nearly everything on the wing--courting, mating, feeding by snapping up insects in midair, and drinking by swooping over water and scooping up a beakful. They even gather nesting material while in flight.

In Monroe, the birds swarm into an old, unused chimney that's part of the Frank Wagner Elementary School. The chimney is 31 feet tall with an opening that measures four square feet. As many as 21,000 swifts funnel into it in a matter of minutes. Once inside, each bird jostles to find a holdfast. They settle into place, overlapping like shingles on a roof.

We visited the swifts in September 2014, arriving early to enjoy a feast of spaghetti and apple crisp. (A swift eats about 20,000 insects in a day, so we didn't save any for the birds.) Kids pitched beanbag swifts into a cardboard chimney. People wandered about wearing headbands adorned with paper swifts bobbing on pipe-cleaner posts. An Audubon table lined with stuffed remains of various bird species attracted a small crowd.

Looking at the fragile form of the Vaux's swift, you couldn't help but marvel at its diminutive size and realize just how much of a live bird consists of flurry, fluff, and motion.

Early-birds fluttered near the chimney as evening advanced. The sky darkened, and the swifts' numbers grew. They looked like bats as they flickered through the air.

Darker and darker grew the sky, faster and faster whirled the birds. And then, as if at a signal, they began dropping into the chimney. Each bird dove at the opening, braking its fast forward motion to plummet in tail-first.

So many birds! It was as if the chimney were a vacuum drawing them in from the sky. They twirled in like a reverse cloud of smoke. The tornado spun for several minutes before diminishing, bit by bit, until the storm was down to just a few stragglers.

And then, after a few beats, one last bird zipped across the sky and ducked in just in time, accompanied by onlookers' laughter and applause.

John James Audubon doesn't appear to have ever painted the Vaux's swift, but he did encounter its eastern cousin, the chimney swift, and study its natural history. He witnessed the birds' flowing into a communal roost at dusk and described it :

"When about to descend into a hollow tree or a chimney, its flight, always rapid, is suddenly interrupted as if by magic, for down it goes in an instant, whirling in a peculiar manner, and whirring with its wings, so as to produce a sound in the chimney like the rumbling of very distant thunder."

Ornithologist William Leon Dawson (1873–1928), who called the Vaux's swift a humble "sky-scooter," notes that "at favorite seasons the birds cross and recross each other's paths in lawless mazes and fill the air with their strident creakings, while here and there couples and even trios sail about in great stiff curves with wings held aloft."

Vaux's swifts are a cause for celebration at a number of chimneys along their migratory flight path. You can cheer them on in Monroe this year on Saturday, September 12 (find out more on the Swift Night Out website here). The website also streams images of the birds inside the chimney via the Swiftcam (shown below).