Looking back at all the records for the past 15 years, the odds of discovering a gynandromorph in a bird-banding operation seem to be “almost exactly one in a million,” Bystrak said in an email.īut there’s a caveat to those long odds. Geological Survey that serves as the central clearinghouse for data from bird banding operations across the country. “That bird is quite famous,” says Danny Bystrak, a wildlife biologist at the Patuxent Wildlife Research Center’s Bird Banding Laboratory, in Maryland, a branch of the U.S. “Just watching everyone else react-it was like pure joy.” One in a million?

“I think this time around I have more knowledge about just how rare this is,” she says. The only other bird with bilateral gynandromorphy Lindsay says she’s seen during the past 15 years was also a rose-breasted grosbeak. In fact, since Powdermill began keeping records nearly six decades ago, Lindsay says, only five of roughly 800,000 captured birds have been documented as likely gynandromorphs. ( Learn more about how butterflies with the condition develop.) And bilateral gynandromorphy is different from hermaphrodism, in which an organism has both male and female reproductive organs but may appear on the outside to be either male or female.Īlthough hermaphrodism is natural among many creatures, such earthworms and snails, gynandromorphy is rare and, in birds, seems to occur when cells fail to divide properly early on in development. While gynandromorphy simply means that an animal has both female and male characteristics, bilateral gynandromorphs often appear more dramatically different because those characteristics are separated down the middle of their body the separation may be internal as well as external. Measurements also revealed that the bird’s right wing was slightly longer than the left, typical of the difference between male and female grosbeaks. “There was no question about it,” says Annie Lindsay, bird banding program manager at Powdermill. When they saw the robin-size songbird’s split coloring, it was immediately clear that the grosbeak was what scientists call a bilateral gynandromorph-an animal that appears half male and half female. It had the bright scarlet feathers of a male grosbeak on one side of its body and the canary yellow plumage of a female on the other.

Researchers with a team monitoring bird populations at Powdermill Nature Reserve, in Rector, Pennsylvania, netted a surprise on September 24: a rose-breasted grosbeak with bizarre coloring.

Songbird animal