There's a little island in the St. Louis River Estuary between Minnesota and Wisconsin that's almost completely covered with thousands of white ring-billed gulls.
For decades, in the middle of this teeming, screaming mass of birds, scientists and wildlife managers have worked to preserve another bird — the common tern — one that's threatened in Minnesota, and endangered in neighboring Wisconsin.
Shoreline development around the estuary has destroyed nearly all suitable nesting habitat for the tern. But this tiny island, created in the 1930s with sediment dredged from shipping channels, has created a man-made solution to a human-caused problem.
Every four or five days in the early summer, Fred Strand steers a little motorboat across the St. Louis River Estuary to Interstate Island. Over the past 30 years, he said, he figures he's taken about 500 trips to this little pile of sand and gravel that sits squarely between Duluth and Superior, Wis.
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The island itself is only about 5 acres — about the size of four football fields. And almost every foot of it is covered with ring-billed gulls. There are about 7,000 breeding pairs there this year, plus a few fuzzy gull chicks that have already hatched.
The birds are about the size of pigeons, with white backs, gray wings and a black ring around the tips of their bills. This time of year — just as hatching season begins — their small, spotted eggs cluster in the shallow cups of nests in the sand.
When Strand, who used to work for the Wisconsin Department of Natural Resources and now volunteers for its Minnesota counterpart, and Annie Bracey, a graduate researcher with the Natural Resources Research Institute at the University of Minnesota Duluth, visit the island, they wear hard hats to protect their heads from swooping gulls and towels on the backs of their necks. Poop protection.
But in the middle of this squawking, flapping mayhem, there's an oasis of relative calm. At the center of Interstate Island, Strand has built a series of narrow runways separated by string to provide a safe place for its common terns to nest.
A few gulls make it through, but the terns are smaller and can more easily navigate the string. About 160 pairs of them are nesting on the island this year.
Without the protection of his string runways, Strand says the terns wouldn't stand a chance, because gulls eat their eggs and even their chicks.
"They're a nest site competitor," he said. "They return earlier in the spring than the common terns do, and begin nesting earlier. They'll use the same habitat."
Thirty years ago, the Minnesota DNR cleared Interstate Island's vegetation to expose the sandy habitat terns need to nest. And it worked. But it also created a perfect nest site for gulls. As many as 13,000 pairs have nested in recent years.
The rivalry between the terns and the gulls has recently intensified because high water levels have submerged part of the island. Now, they're competing for even less space.
That's a big problem for terns, because Interstate Island is home to one of only two tern colonies in all of Lake Superior. The other is in Ashland, Wis., also on a man-made island, which provides protection from predators like mink and weasels.
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This summer, Strand and Bracey are capturing and tagging 10 pairs of breeding terns and their chicks as part of a longstanding effort to monitor and track terns. They're outfitting them with radio transmitters so they can track their migration.
The traps they use to capture the birds are very low-tech. Strand props a mesh box up over a nest with a stick with a string tied to it
"And when the birds return," Bracey said, "they'll walk right under it and sit on the eggs, and once they sit down he can just pull the string, and then he'll walk up and take the bird out with his hand."
Strand holds the bird steady while Bracey takes a tiny blood sample, places a small band around its leg, and loops a little harness she designed herself up the bird's legs, which secures the radio transmitter's antenna to the bird's back, hidden in its tail feathers.
After about 10 minutes, Bracey releases the bird and it quickly flies away. "Good luck, friend!" she calls after it.
These birds migrate all the way to Peru, about 4,000 miles from this island in the estuary, and then return, sometimes to the exact same nest. The transmitters will allow researchers to track the birds during their journey, to glean information about when and where they stop, and how long the parents stay with the young birds.
The goal is to try to get some clues about why the tern population worldwide is declining.
Here in Duluth, their numbers have held fairly steady. But that plateau has taken a lot of work, because they've lost nearly all of their natural habitat. For three decades, Strand has helped maintain the nesting site on Interstate Island. He marks the nests and bands every single chick to monitor the population.
He admits terns are a "high-maintenance species." But, he said, they're worth it.
"As a parent myself, I admire their tenacity to their eggs when they're laid to their nest site, and for caring and taking care of their young," he said.
Strand says ring-billed gulls aren't the bad guys in this drama.
"That's the gull that we see on parking lots, at your picnic table, on the golf courses, in the farm fields," he said. "We've created a lot of great habitat for them, and they're doing very well."
At the same time, human development has taken away most suitable tern habitat, he said.
"So we're part of the cause, but we can be part of the solution, too," he said.
That solution includes a $1.1 million project to build up Interstate Island to protect it from future flooding, part of the broader effort to restore the St. Louis River Estuary. That work is expected to begin next year.