- Associated Press - Monday, June 22, 2015

ISLE, Minn. (AP) - Hennepin Island - a jumble of boulders left by the glaciers and rearranged by shifting lake ice - is remote, wave-ravaged and populated by ring-billed gulls poised for a take-over.

But year after year, a colony of common terns returns to nest on a slice of this quarter-acre island. It’s part of the two-island Mille Lacs National Wildlife Refuge, which turns 100 this year. Smallest of the nation’s 563 refuges, the islands together comprise 0.57 acre originally set aside to protect colonial nesting birds.

Today, Hennepin Island is one of five common tern colonies in the state, the St. Cloud Times (https://on.sctimes.com/1MQE3KR ) reported. Minnesota supported an estimated 2,000 breeding pairs in 1900, according to the Minnesota Department of Natural Resources. That estimate dropped to 880 by 1984.

In Minnesota, the sleek white bird is listed as a threatened species and a species in greatest conservation need. The U.S. Fish & Wildlife Service lists it as a conservation priority for the region.

About 1,000 pairs, one-tenth of the Great Lakes population, are thought to nest in Minnesota. With about 225 pairs, Hennepin Island is among the most productive sites. The others are in the St. Louis Estuary near Duluth, Leech Lake, Lake of the Woods and the Northwest Angle.

Hennepin Island’s success is mostly due to the lack of predators (great-horned owls, fox and mink among them), the abundance of minnows, and the dump truck loads of pea gravel that cross the ice to replenish the “beach” side of the island every five years. Terns lay their eggs, usually four per clutch, in depressions in the gravel.

“We sometimes call them the uncommon common tern,” said Kelly Applegate, Mille Lacs Department of Natural Resources wildlife biologist and fisheries technician.

“If we were to stop all management, we would probably lose the tern colony within the season. There would be no room for them because the gulls would out-compete them,” Applegate said.

The grid that keeps gulls out of tern nesting habitat wasn’t yet erected June 2 when Walt Ford, who manages the Mille Lacs and Rice Lake national wildlife refuges, led a boat tour circling the islands. (Boats aren’t allowed within 200 feet of the island.)

“Just look at this abundant bird life on this little piece of rock,” Ford said.

Terns rose above Hennepin Island like a cloud of origami creations. Ford likened their appearance to stealth fighters, with their backswept wings and ability to hover over the water. Caspian terns, pelicans and gulls were among the other species on and around the island.

Mille Lacs - including tribal, state and federal land - is among Audubon Minnesota’s 57 Important Birding Areas. IBA Program Manager Kristin Hall said waterbird diversity is the reason for the designation. More than 230 bird species have been documented there.

Active common tern management began on Hennepin Island in 1993. During the summer, Mille Lacs NWR and DNR staff take turns making weekly visits.

Anchoring the boat and wading ashore, they pound thin metal posts that will hold the grid into the rock. Two-foot openings in the taut plastic line deter gulls but are easily accessed by the agile terns. (Coating gull eggs with vegetable oil is another tactic that keeps the gull population down.) From early June into August, they’ll check the grid; count nests, eggs and chicks; determine chicks’ age; and determine fledgling rate.

Applegate said the birds are accustomed to the intrusion and hover nearby.

“They’re extremely graceful fliers, and a lot of times they’ll be flying and floating above the water - about 10 feet off the water looking for minnows, hunting,” Applegatae said. “Then they’ll just tuck their wings and kind of dive into the water and - boom - they’ll catch a minnow, and then they’ll bring that to their young.”

Common terns are persistent - if not the most successful - nesters. At age 2 or 3, the birds will return to Hennepin Island from the Gulf. Most won’t successfully breed the first year back; they’re most productive at age 5.

The per-pair fledgling rate is less than 0.5 chicks a year. The most successful year was 2007, with a fledgling rate of 1.08 per pair. The Minnesota Department of Natural Resources’ management goal, unchanged since 1994, is 1.1 fledglings per pair.

They’ll re-nest as late as August. Another setback is the long incubation period. Eggs take about a month to hatch.

“There will be times where there will be several hundred eggs ready to hatch, and if we get a bad storm with high winds it can be devastating. The next time we go out there, the eggs will be gone or they will be washed up on shore,” Applegate said.

While management continues on Hennepin Island, research by University of Minnesota graduate students overseen by Francie Cuthbert, a fisheries and wildlife professor whose career has focused on water birds, is tracking common terns.

Student Annie Bracey is collecting date from geolocators, which track movement based on light levels. That information will more precisely show where the birds that nest on Interstate Island near Duluth spend the winter and the stops they make during migration.

“Because common tern numbers are low and they are declining in different parts of their range, it’s important to understand is this something that’s happening during the breeding season, or are they under certain threats during the winter,” Cuthbert said.

Meanwhile, the Mille Lacs DNR and NWR are working to establish a more hospitable nesting habitat - on two modified pontoon boats that would be anchored in calmer waters of Lake Mille Lacs.

A $23,000 Circle of Flight grant the Bureau of Indian Affairs awarded to the Mille Lacs Band of Ojibwe in February will allow the agencies to buy the pontoons, modify the decking and install safety features making them visible to boaters.

Applegate said Central Lakes College students might be tapped to make decoys. Audio recordings would help attract common terns to their new nesting pads. Target launch date is next spring.

“We want to get them away from the dangers out there,” Applegate said.


Information from: St. Cloud Times, https://www.sctimes.com

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