Over the last two weeks in August every year, Steve Kolbe climbs onto the roof of an apartment building in eastern Duluth and stares at the sky.
He’s up there for only a few hours each evening, from 5 p.m. to sunset, but what he sees is often unparalleled in the world of bird migration: hundreds or even thousands of nighthawks flying south.
“I don’t consider a real 'flight’ until it hits 1,000 in an evening, and that happens fairly often,’’ said Kolbe, a researcher at the Natural Resources Research Institute of the University of Minnesota Duluth.
Kolbe’s top evening this year, Aug. 24, saw an estimated 20,000 nighthawks.
“There’s really nowhere else in the world where you can see anywhere near that many nighthawks. For most of the summer, they are pretty territorial, spread out and hard to find, let alone count,’’ Kolbe said. “But they are obviously very social in migration, and this is by far their busiest migration route that we know of.”
Like most other migrating birds in the region, the nighthawks funnel over Duluth as they avoid flying over Lake Superior on their marathon northwest-to-southeast migration.
Kolbe is so fascinated with nighthawks that they are one reason he moved to Duluth after graduating from Miami University in Ohio. He landed a job counting hawks at Hawk Ridge in 2014 and now has moved on to graduate studies at NRRI, focusing on nighthawks.
From some limited GPS tracking efforts, many of the nighthawks flying over Duluth each fall appear to be coming from northwestern Canada — Alberta and British Columbia — on the way of one of the longest migration trips of any bird in the world. They will spend their winters in South America.
Oddly enough, not many nighthawks fly back over Duluth in spring. They take another, more westerly route on their way north, Kolbe said.
“We really don’t know much about where they are coming from or where they are going to,’’ he noted. “Some of them winter in the Amazon valley jungle.”
Across the Americas, it’s widely believed that nighthawks, which eat only flying insects, are in steep decline, along with other insect-eating birds like swifts and swallows. One estimate put the annual decline at 6%, severe enough to be considered a death spiral for a species.
Researchers are concerned that a decline in birds that eat flying insects may be an environmental indicator of something more severe going on a large scale, the global food chain of insects and their predators.
But 13 years of nighthawk counting by NRRI personnel has found no noticeable decrease in the migration over Duluth. The annual count here “fluctuates a lot depending on the weather. But over the long term, we’ve seen an insignificant increase, not a decrease. We don’t know why that is,’’ Kolbe said.
The nighthawk migration over Duluth happens almost entirely between Aug. 15 and Sept. 1 each year, although some may trickle through for another week or so. This year’s total count will approach 30,000, Kolbe said, about midpoint between low years around 15,000 and high years of 45,000.
On Aug. 26, 1990, Mike Hendrickson, an experienced counter, tallied 43,690 nighthawks in a two-and-a-half-hour period — the highest single-day count ever near Duluth.
Nighthawks often appear to be feeding in the evening, seen in swirling flocks, and then make their serious migration miles at night, Kolbe noted.
The common nighthawk is a jay-sized bird about 10 inches in length, medium-sized, slender with long, pointed wings and medium-long tails. Only the small tip of the bill is usually visible, and this combined with the large eye and short neck gives the bird a big-headed appearance. They can’t defend themselves against potential predators, but they are well-camouflaged to avoid detection when they roost.
The name “nighthawk” is a misnomer, since the bird is neither strictly nocturnal — it’s active mostly at dawn and dusk — nor closely related to hawks. Nighthawks are members of the nightjar family that includes whip-poor-wills and the common poorwill, and a distant relative of owls.
They feed entirely on insects, and only by flying fast and swallowing the insects whole in flight — right down the gullet, no chewing — which is why they have their mouths open almost constantly when hunting.
As daylight hours begin to diminish in northern climes, signaling a decline in insects available, nighthawks head south fast, one of the first major pushes of migrating birds each autumn.
They also leave early because they have a long way to go — one of the longest migration routes of any North American bird. Most travel over land through Mexico and Central America, although many do pass through Florida and Cuba, island-hopping to reach their wintering grounds in South America.
Source: Cornell Lab of Ornithology