There's a fly in the ointment of crane recovery

It's taken hundreds of people, nine years of time and up to $16 million in public and private funds to give the whooping crane an extended lease on life. Now the program, which is based in central Wisconsin, could be threatened by a tiny insect: the black fly.

Black flies are attacking the cranes that have been nesting at the Necedah National Wildlife Refuge, about 75 miles northwest of Madison. The embattled cranes have fought back the only way they can: by leaving. When they do, they abandon their eggs.

That means the effort to establish a second wild flock of whooping cranes may be as endangered as the cranes themselves.

Whooping cranes were once found in 35 states, Canada and Mexico. About 70 years ago, hunting and loss of habitat pushed them to the edge of extinction. But in the early 1950s, biologists started a restoration effort, which included establishing a stationary flock in Florida and rebuilding a migrating flock in the west.

The flocks held their own, but having only one migratory flock was considered risky. Any catastrophic event -- such as a late spring or a oil spill -- could wipe out a single flock.

So, to help ensure the future of the species, the Whooping Crane Eastern Partnership was founded. The goal of the partnership -- which involves three federal agencies, seven state DNRs, 18 nonprofit groups and dozens of corporate sponsors -- is to establish a second migrating flock in the Midwest. (Sites in Minnesota were considered, but Necedah was chosen.)

The Wisconsin flock (called the eastern flock) has been built slowly and carefully with hand-raised birds. Eggs are taken from captive Florida cranes and incubated artificially at a research center in Maryland. The hatchlings are brought to Wisconsin to mature under close supervision.

Because cranes need to fly their migration route once to implant it in their memory, the Wisconsin birds have learned that route by following ultralight aircraft to Florida. The cranes are introduced to the sound of an ultralight's motor before they hatch. The sound of the planes becomes the sound of "mom."

The plan is to have at least 40 nesting pairs of cranes in the western flock and 25 pairs in the eastern (or Wisconsin) flock. The adult cranes at Necedah are doing their best. The have mated and laid eggs. Last spring, 12 breeding pairs began incubating eggs. But the birds abandoned their eggs.

Focus on flies

There could be several reasons the cranes are leaving their nests. Their diet could be an issue. These relatively young birds also could be inexperienced at nesting. There could even be genetic problems, since the entire restoration effort began with just 15 birds.

But Jim Leach, federal wildlife refuge supervisor for Wisconsin and Minnesota, said the crane team suspects that black flies are to blame.

"In my view," said Leach, "we've established a migratory flock."

Unfortunately, it's a flock that can't increase its numbers because the birds have been forced to abandon their nests.

Two black-fly experts from Clemson University are now working with the crane team to develop a treatment program. There is a possibility that a bacterium, known as Bti, could be the solution. Bti, which attacks the larval stage of the fly, could be applied to the fast-flowing streams where the flies hatch.

"We want to see if suppressing the fly population is effective, or should we look at other factors," said Louise Clemency, a Wisconsin field supervisor for the U.S. Fish and Wildlife Service. "There's a lot we don't know about whooping crane breeding biology."

But a few things are clear: The survival of the whooping crane is not guaranteed. And finding no solution to the nesting problem would be tragic for the birds and those of us who care about them.

"Solving the nesting problem" Clemency said, "is crucial."

Jim Williams, a lifelong birder, is a member of the American Birding Association, Ducks Unlimited, Pheasants Forever and Delta Waterfowl. Join his conversation about birds at www.startribune.com/wingnut. He can be reached by email at two-jays@att.net.