NECEDAH - A bug bite often causes you a little itch, and a little discomfort.
For endangered whooping cranes, the bite of black flies causes something more serious.
It's making hatching eggs very difficult.
For a population already in danger, that's a big problem.
"The population has not been able to produce enough offspring to be sustainable over the long term," says Dr. Brad Strobel, a Wildlife Biologist at the Necedah National Wildlife Refuge in central Wisconsin.
The refuge includes a handful of only about 400 surviving whooping cranes in North America.
We found some on a visit to the Necedah National Wildlife Refuge.
But if something doesn't change, this endangered species could be in even more danger.
"It's pretty paramount that we start evaluating multiple different hypotheses and try to find a solution as quickly as possible," says Strobel.
Adult migratory whooping cranes are doing pretty well here.
A group called the Whooping Crane Eastern Partnership re-introduced a migratory branch of whoopers a little more than decade ago.
The goal is to provide diversity among the cranes in North America.
Necedah had been a near-perfect nesting habitat for this newer group of birds.
"One of the biggest components that Necedah has for nesting whooping cranes is a large complex of wetlands. They prefer emergent wetlands that have sedges or grass-like vegetation growing up in them. That's what they construct their nests out of," says Strobel.
The adult population is low, but stable.
The problem - the adults aren't reproducing effectively.
Wetlands like the ones abundant at Necedah are optimal places for whooping cranes to nest and to live.
They sure need it.
Only a couple hundred of the species exist in the United States as an entire population.
But the black fly, this new pest, is something that's making places like this, places like Necedah, a little bit less desirable for many of the whooping cranes to nest.
Tiny black flies emerge into Necedah and pester whooping cranes and their eggs, literally swarm and bite them, during the incubation period.
This spring, just like years past, whooping cranes have had enough with the pests.
"All of the nests on federal property had abandoned. All of the 16 we'd been monitoring here," Strobel says.
While the eggs are then incubated artificially, it's not the same, and it's certainly not sustainable.
Several groups just finished a four-year study of the problem.
"Functionally, it comes down to three potential options," says Strobel.
One, keep the flies away.
Two, have the birds avoid the flies, either by going to a different space, or by nesting at a different time.
Three, improve the birds' tolerance for the flies.
"The most important component about this population is making sure that it's self-sustaining," Strobel says. "Being migratory, being able to avoid predators, and reproducing well."
Scientists still don't know which option is best.
They're hopeful they can help the cranes by next spring.