An adult whooping crane raised under a federal "foster nest" experiment has died in an apparent collision with power lines.

The rare bird was found dead last Sunday on private land eight miles east of Monte Vista in the San Luis Valley of southern Colorado, said Rick Schnaderbeck, assistant manager of the Monte Vista National Wildlife Refuge.It was believed to be a 15-year-old female reared under the foster-nest program that ran from 1975 to 1989, Schnaderbeck said.

The dead bird was one of two foster-nest whoopers that wintered at Bosque del Apache National Wildlife Refuge south of Socorro, N.M., U.S. Fish and Wildlife Service spokesman Hans Stuart said Friday. A third foster-nest whooper that wintered near Bernardo, N.M., north of the Bosque, is in the San Luis Valley as well, he said.

Two juvenile whooping cranes also remain in the San Luis Valley. The juveniles are from another experiment, in which a researcher in an ultralight plane led whoopers south from Idaho to New Mexico last fall.

The juvenile whoopers migrated north last month without human intervention for their stopover in Colorado. The stopover typically lasts about a month. The whoopers are expected to return to Idaho soon.

Researchers for years have tried to get endangered whooping cranes to migrate to new habitats to help establish a second migratory flock. The only existing migratory flock of whooping cranes winters at Aransas National Wildlife Refuge on the Texas gulf coast and summers in Canada.