Roxie Laybourne, who spent her career at the National Museum in Washington, was one of my mentors. Among her claims to fame was that she was the only person who could identify the sex of a living Whooping Crane.
Whooping Crane sex is important. The Fish and Wildlife Service took eggs from wild nests in Canada and hatched them in Maryland. They bred these birds to build a captive flock, thereby assuring survival of the species in case anything happens to the wild birds (oil spills, late season hurricanes?).