WEST ALTON • Ben McGuire walked gingerly around the perimeter of the man-made sandbar, being careful to step over any eggs.
Interior least terns circled overhead, protesting in a squeaky sort of song. The females wanted to get back to their roosts. Later, they only left their nests to dip into the backwaters of the Mississippi River so their eggs wouldn't get too hot.
Last week there were five nests with a total of 15 eggs. McGuire placed a rock painted with a number next to a new nest depression in the sand and quickly returned to his boat.
According to the timer on his watch, he'd kept the birds away for about nine minutes, well under his 30-minute limit.
McGuire, 26, is a wildlife biologist with the Army Corps of Engineers, which is in its fourth year of a five-year experiment to help increase the number of interior least terns — an endangered species.
The current interior least tern population is about 15,000, more than double what it was in 1995, but it remains endangered.
The birds, which are about the size of robins and have distinctive white patches on their foreheads, are in the same family as seagulls, he said. They feed on small fish and roost in open ground on sandy beaches and small gravel.
They lay eggs along rivers, and that has led to their decreased numbers. Humans have unknowingly destroyed their nests. Predators such as raccoons, possums, skunks and minks have taken out large numbers of their young.
"The biggest thing though, has been a loss of habitat because of dams, channelization and other changes to river systems," McGuire said.
MAN VS. NATURE
Because interior least terns often roost on federal land, the corps is mandated to manage them, McGuire said. Officials also feel a responsibility to help because their work along the waterways may have hastened the decline of the species.
Charlie Deutsch, another wildlife biologist with the corps, said this type of tern hasn't had a successful colony in this area since 1960, so in 2002, they began to work to change the situation.
The corps built an island in Ellis Bay, but for unknown reasons, the birds never used it.
Seven years later, biologists gambled on a floating habitat, an idea that had been successful with other species of terns elsewhere in the U.S.
Workers used cables to lash together two old pontoon barges that had been used for dredging operations. They covered the 1,500 square feet with a few inches of sand, some driftwood and decoys.
A lattice-work roof made of rope discourages predators, and wooden shelters give new chicks refuge from the sun.
They positioned the barges just upstream from the Melvin Price Lock and Dam and adjacent to the Riverlands Migratory Bird Sanctuary. Two 1,000-pound anchors keep them in place.
Startup costs for the project were about $20,000, mainly to retrofit the barges, but now the annual cost is about $500 for material and maintenance.
The first year, the project was successful. About 36 adults used the habitat to hatch 30 chicks.
Subsequent years have been a struggle. In 2010, about 50 birds came to breed, but a blue heron saw the nests, landed on the edge of the barges and walked under the latticework to get to the chicks. It ate about 25 young, McGuire said.
"We saw the heron, but it was already too late by the time we could get out there on the boat," he said.
The next year, the corps added a fence around the perimeter to prevent another blue heron attack, but only about six birds nested and laid five eggs. Before workers could band the young this time, they disappeared overnight.
McGuire said he doesn't know if they left on their own or a predator got them.
PROJECT'S FUTURE IN DOUBT
A few weeks before the birds began to nest this month, McGuire went out to check on the habitat and hook up a solar panel to power a tern call box to attract the birds.
"It's an effort to convince them that there's a colony already established here," McGuire said. The corps also uses a webcam with a live feed and infrared so they can observe the birds at night. An intern keeps tabs on the activity.
Once nests have been spotted, McGuire tries to avoid disrupting the birds. He usually only goes out to count nests and the speckled eggs once a week.
Since the incubation period is about three weeks, McGuire said the trick becomes timing the visits to band the most birds possible before they fly away.
The birds nest as far north as the Dakotas, and they migrate to Central and South America. It can take them two years to return to a breeding area.
None of the birds banded in the local project have returned, but McGuire remains hopeful.
The birds live for 12 to 14 years, giving even a small project like the corps' the ability to have an impact on the population, he said. Changes in management of the rivers also has helped the species to rebound, he said.
The future of the corps' project past next year is still undecided, in part because of problems with predators.
"If it's successful, then we'll continue it and hopefully get bigger barges," McGuire said. "And if it's not successful we certainly don't want to contribute to the decline of the population."