Effort to protect, track nesting terns in harbor turns up surprising results
Amid the swarming, screeching, stinking mass of 40,000 or so ring-billed gulls, 180 nesting pair of common terns are hurriedly raising their chicks on Interstate Island in the middle of the Twin Ports harbor.
The chicks that hatch and survive to 25 days old should be strong enough to fly south with their parents in a few weeks, all the way to the west coast of Peru, to spend the winter.
Those that can't fly by then are out of luck. The adults will leave without them if they aren't ready by Aug 1, when the urge to migrate overrules the urge to raise their young.
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"If you are a tern chick, you want to be part of an early hatch. If they are just hatching now, their chances of surviving are nonexistent," said Fred Strand, a retired Wisconsin Department of Natural Resources wildlife manager now volunteering his tern expertise for the Minnesota DNR.
Most tern chicks hatch in late June and early July, after their parents spend 21 days incubating the eggs. If at least one chick from each nest makes it to fly south, the colony can maintain its population. If a storm comes, or spring is too cold, or if a predator makes it onto the island, the entire colony's hatch for the year can be wiped out.
"There's a lot that can go wrong,'' Strand said. "But they are managing to hang on here."
Thanks to a lot of help.
Strand has been monitoring, counting, banding and helping terns nest on Interstate Island for 25 years. The Twin Ports colony, which has stabilized in recent years, is among the largest in Minnesota and Wisconsin.
Not so common
While the name implies abundance, common terns are called common only because they once were widely distributed. There are very few of them remaining in the Midwest, with the only other major colonies in the region at Mille Lacs Lake, Leech Lake, Lake of the Woods and the Ashland harbor. They are listed as endangered in Wisconsin, threatened in Minnesota and a species of concern across the U.S.
"What you see right here are 60 percent of the terns on Lake Superior. The other 40 percent are in Ashland. There aren't any others," Strand said as one of the black-capped, orange-footed, orange-billed adult terns hovered above his head.
Members of the tern team wear hard hats, not just to keep guano out of their hair, but because the adult terns will peck at invaders' heads as a warning to get away from their nests or chicks.
On this trip to the man-made island that straddles the state line between Minnesota and Wisconsin, Strand was with Martha Minchak and Bruce Anderson, assistant Minnesota DNR wildlife managers, and Annie Bracey, a bird researcher for the Natural Resources Research Institute at the University of Minnesota Duluth.
The local tern team has been working for years to maintain tern habitat — sandy, rocky and free from nearly all vegetation — in the middle of 6-acre Interstate Island, now a Minnesota State Wildlife Management Area. But the island is both sinking and eroding, thanks to a rising Lake Superior and flood-prone St. Louis River. That's made it smaller, and packed gulls, terns and Canada geese are nesting closer together.
"We got some sand spread out here to try to improve the nesting area for terns. But we could use a lot more. We'd like to get at some of the dredge material (from the harbor) if we can work it out,'' Minchak said.
Wildlife managers have for years been erecting chicken-wire fencing in rows to create safe nesting areas for the terns. This year they rebuilt the protective runways. They also hang string over and along the rows at just the right width to discourage gulls form trying to fly in.
"It's wide enough apart for the terns to fly down through, but the gull wings are wider so they don't like it," Minchak said as the team "wrangled" tiny fluff-ball chicks to band them, registering each one's number for future reference.
Around the 15 runways of tern fencing is a no-man's land, also enclosed in chicken wire. Any gulls that try to nest there are shooed away and their nests destroyed, creating a buffer for terns.
For the most part, it works. Most gulls don't go into the tern areas. And the tern chicks can't wander out into the mass of gulls where they would face instant death.
Banded with bling
This year, more than 300 tern chicks managed to hatch among the 180 nesting pairs of adults. And researchers now are busy banding each one, giving it a number so they can be tracked in years to come.
"The parents don't like us in here. But we minimize the handling time, and they are always back with the chicks in 5-10 minutes," Bracey said.
Several of the adults get even more jewelry. About 35 Interstate Island terns have carried geolocators since 2013, devices that can track their long travels by sunlight and clock. And another 10 terns are carrying tiny GPS devices.
Researchers each spring try to recapture the blinged birds to recover the data; the birds aren't big enough to carry GPS units that can transmit data. And they have documented an incredible flight pattern.
The Twin Ports terns first head east, to Lake Erie, then farther southeast to the Carolina and Florida coasts. Then they head to western Central and South America, where the chicks will spend two years and the adults will spend the winter.
They show up back in the Twin Ports in May. They usually arrive after the gulls, so crews try to have shooed the gulls out of the tern area before the smaller birds arrive.
It's an annual, ongoing effort to keep a rare bird, with picky nesting preferences, from fading into oblivion.
"Because common terns are declining in the Great Lakes Region and are listed as threatened in Minnesota and endangered in Wisconsin, understanding where these birds migrate and winter has important conservation implication," Bracey said. Knowing where they spend their time away from their summer home will help determine what wintering and migration areas are critical to support the Great Lakes tern population.
The local tern effort is a team effort. Funding comes from the Minnesota DNR's Nongame Wildlife Fund, the Minnesota Lake Superior Coastal Program, Minnesota Ornithological Society, U.S. Fish and Wildlife Service, Natural Resources Research Institute, the Duluth-Superior Area Community Foundation's Biodiversity Fund and the University of Minnesota.