On a warm late summer evening this week, Steve Kolbe stood on the roof of a three-story apartment building on the far eastern side of Duluth, his eyes glued to binoculars, his head on a swivel, studying the blue sky for tiny specks on the horizon.
After about 20 minutes, he finally spied what he was looking so intently for. "There's a nighthawk right here,” he said, as the birds materialized seemingly out of nowhere.
"OK, so we got a little flock going here. So there's 25. And then there's another group going over."
Kolbe counts quickly, his mouth silently forming the numbers. When there's a lull he enters them in a tablet, and then starts over again at zero.
It doesn't seem too tricky for a couple dozen birds. But Kolbe has counted as many as 14,000 nighthawks in one three-hour stretch.
"It's just like how you would count anything else, you sort of tackle it as methodically as possible, as efficiently as possible,” he explained. “And with very rare exceptions, there's maybe only been a few moments of a few flights over the years that I haven't counted every bird one by one."
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For two weeks at the end of every summer, thousands of nighthawks fly over Duluth like clockwork, during their marathon migration to South America. It's the largest known migratory concentration of the common nighthawk in the world.
And for the past eight years, Kolbe, an avian ecologist at the Natural Resources Research Institute at the University of Minnesota Duluth, has counted just about every one of them.
“It’s an amazing spectacle, it doesn't happen really anywhere else,” he said, as a hummingbird whizzed past. "The numbers of nighthawks that we see here are not matched anywhere else in the world.”
The reason is Lake Superior. Birds don't like to fly over it. So when nighthawks from all over western Canada migrate south and east, they eventually hit the big lake, and when they do, they veer to the right, eventually flying over Duluth — and over Kolbe, perched on this roof just a couple blocks off the lake.
He's here every night during the last two weeks of August, from 5 p.m. until sunset. Over the years he’s helped convert several of the residents into birders, including Charlie Nelson, who came up to the rooftop to check out the nighthawks circling overhead.
“Oh, geez, look at that,” he exclaimed. “Holy smokes look at them all up there."
Nighthawks are not actually hawks at all. They're aerial insectivores, like the whip-poor-will. They eat bugs. And on this evening, they took a break from their long journey to forage in the sky above where the Lester River flows into Lake Superior, swooping and careening around like bats.
"There's something about this birding, that's addictive,” said Nelson. “[Kolbe] can tell me all this interesting stuff about all these different birds and what they do and why they're doing what they're doing. It’s a never-ending experience of wonder."
Kolbe has felt that wonder for as long as he can remember. Even though he witnesses it every year, he said he’s still amazed that many of the nighthawks just hatched this spring. They’ve never migrated before. Yet year after year they travel the same route over Duluth.
“It's like there's signs telling them where to go,” he said. “They have such clarity to their world and their lives. It seems like they know exactly what they ought to be doing and sort of trust their instincts. They're on a mission to do something. I find that really, really compelling to watch.”
This is the 14th consecutive season UMD ornithologists have counted common nighthawks. Those counts provide a snapshot of how the species is faring. And every year they do it, the data gets more valuable — the trends they’re seeing get more refined.
Kolbe typically counts between 20,000 and 25,000 nighthawks a year. And that number has held steady, which is a little surprising.
That's because populations of insect-eating birds, like nighthawks, swifts and swallows, are declining around the world, as the number of insects plunges because of factors like habitat loss and the application of pesticides.
The Minnesota Department of Natural Resources has listed the common nighthawk as a species of concern.
"In Canada, the population is supposed to be declining 6.6 percent per year, which is basically the floor falling out,” Kolbe said. But he’s not seeing that trend reflected in the annual migration over Duluth.
“And it seems like if that was happening in this population that we sample, we would see it over 13 years.”
There could be a lot of reasons for that, said Alexis Grinde, who manages the avian ecology lab at UMD’s Natural Resources Research Institute.
One, researchers don’t know where exactly the nighthawks that pass over Duluth are coming from. “We definitely need more information about the general migration ecology to put our counts in context,” she said.
Kolbe suspects that as the count continues, he may begin to see fewer birds.
If that's the case, he hopes to be the one to document it. He's done the math, and figures if he keeps at it, he'll eventually count more than a million nighthawks, one by one.
"It’s certainly one of the joys of my life and things that I look forward to every year a lot. I get a little melancholy this time of year when it starts to wind down."
Nighthawks will continue to trickle through Duluth for the next several days, but Kolbe's official count for the year has ended. The final tally? It’s 20,395 birds.