A conservationist substitutes a whooping crane (Grus americanus) egg for a sandhill crane (Grus canadensis) egg. This was part of an effort, initiated by the USFWS and the CWS in 1975, to raise population levels of the endangered whooping crane by cross-fostering with sandhill cranes. Although 85 chicks from the 289 whooping crane eggs transplanted into sandhill crane nests learned to migrate, the whooping cranes failed to mate with other whooping cranes due to imprinting on their sandhill foster parents. The project was discontinued in 1989. Photographed at Grays Lake National Wildlife Refuge, Idaho.