Most of the time, tree swallows move so astoundingly fast it’s hard to see anything but a blur. They’re in such constant motion they rarely stop long enough to offer more than a glimpse of their deep blue-and-white plumage that looks like a tiny tuxedo.
So I was surprised one windy afternoon last month on the plains of eastern Wyoming when I came across a full dozen Tree Sparrows clinging to a barbed-wire fence. The wind was so strong they were momentarily grounded. When they did try to fly, the wind held them in place for a time as they took off and landed.
It was as if these little aerial acrobats were frozen in the air.
As long as the wind kept up, I had a chance to catch these birds in the midst of takeoffs, landings, feedings, squabbles, gobbles, squawks and occasionally quiet moments of stillness.
Nobody knows these hyperactive birds better than David Winkler, a long-time professor at Cornell University who researched swallows throughout his career before retiring two years ago. He’s still working with his swallows, to his great delight.
“They’re masters of the air,’’ he said. “I never get tired of looking at them.’’
Winkler has studied the swallows’ migration, feeding and mating habits, their flight dynamics and nesting routines. He started toward the beginning of his career as a professor of ornithology, and he found no end to the questions about swallows he hoped to answer.
What he finds most fascinating is their tireless drive, the same thing that makes them so fascinating to watch in flight. “They don’t let anything get in their way,’’ said Winkler.
That was certainly the case on the day of my encounter in Wyoming. Though the swallows did spend more time than they usually do perched, they constantly tried to get back into the air to gather insects that make up the bulk of their diet.
A pair of these birds will gather as many as 10,000 insects a day to feed their young and themselves. They can carry dozens in their beaks as they return from zipping through the air. Then they’d fight, sometimes viciously, over their quarry when they’d come back from a flight.
Tree Swallows are tiny birds, weighing just 20 grams or so, but they have a relatively wide wingspan of up to almost 14 inches. Those long wings reach far down their bodies when folded up, which helps give them the tuxedo look.
They need that flight prowess for more than their endless, circling feeding sweeps during the day. Come migration time each spring and fall, they’ll fly the length of the continent from as far north as Canada’s tundra to the southernmost U.S. and Caribbean. Here’s a map from the Cornell Lab of Ornithology that shows their annual migration in the form of a video over the course of the year.
Tree Swallows are plentiful. The primary survey of breeding birds estimates their population at 17 million in North America. Still, they’ve lost about half of their numbers over the past 50 years and are proving susceptible to changing climates, something that Winkler has studied over the years. He has worked with peers to develop a version of a tracking device to follow their migration paths to figure out what might be contributing to their declines.
Winkler worries about their future, but he says he has lots of faith in the ability of these birds to overcome even the toughest of obstacles.
“You have to remember that they’ve been doing this migration thing for way, way longer than humans even existed,’’ he said. “These animals are very professional, and they’ve been dealing with problems like this for a long, long time.’’