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.