PRAIRIE DU SAC - Wisconsin bird rehabilitator Marge Gibson has released a lot of eagles. Hundreds, she figures.

Always, she says, she misses the birds after nursing them back to health from injuries or illnesses and then letting them go. If only, she has mused in the past, they could send back post cards from their travels.

Monday afternoon, on the banks of the Wisconsin River here, Gibson freed an eagle that actually will keep in touch -- via satellite.

The big 3-year-old female is one of three that Gibson, who operates Raptor Education Group Inc. in Antigo, has nursed back to health from West Nile virus.

Found two years ago not far from where it was released below the Prairie du Sac dam, the eagle nearly died of the disease. When a warden with the Department of Natural Resources found it, the bird was having convulsions.

The female, along with two males Gibson released earlier this winter, are the first eagles to be treated and cured of the virus, which is spread by mosquitoes and can also infect humans.

It's unique and important work and the techniques being used are of great interest, especially because the virus has infected more than 100 bird species and has killed hundreds of birds in the upper Midwest, including red-tailed hawks and great-horned owls. It also threatens endangered birds such as the trumpeter swan.

"It really is a significant contribution," said Jennifer Meece, a Marshfield Clinic expert in West Nile and mosquito-borne diseases, of Gibson's work. "I know she has spent many nights staying up with these birds. She's given them a chance."

Nick Derene, a wildlife graduate student at UW-Stevens Point who is assisting Gibson on the West Nile project, said the work is providing critical new information about how to treat the sick eagles.

Even more important, he said, is the information that will be gained from tracking the eagles once they return to the wild.

Derene said researchers want to find out if the disease has affected the birds' ability to hunt or socialize and mate with other birds. The two males are doing well, he added. One is in Illinois but the other has stayed in the vicinity of the river and has been roosting with a large group of eagles.

Tracking information from the satellite is sent to Derene's computer. "Every night at midnight I get an e-mail telling me where the birds are," he said.

The fate of the female is of special interest, Derene added.

"This will be the bird that will tell us about the impact of West Nile on the offspring," Derene said.

The eagle certainly didn't seem any worse for its ordeal as it spread its wings and glided low over the silver Wisconsin River. It swallowed about a pound of meat before its departure, a bit of insurance that will keep it from having to hunt for food for a day or so, according to Gibson.

"This is an incredible time," Gibson said as the eagle set its wings and soared. "To be releasing these birds after seeing them convulsing and dying, to see them taking their place again in the wild world."