Name: Half-female, half-male rose-breasted grosbeak found in Pennsylvania
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Half-female, half-male rose-breasted grosbeak found in Pennsylvania

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October 9, 2020Researchers with a team monitoring bird populations at Powdermill NatureReserve, in Rector, Pennsylvania, netted a surprise on September 24: arose-breasted grosbeak with bizarre coloring. It had the bright scarletfeathers of a male grosbeak on one side of its body and the canary yellowplumage of a female on the other.When they saw the robin-size songbird’s split coloring, it was immediatelyclear that the grosbeak was what scientists call a bilateral gynandromorph—ananimal that appears half male and half female.“There was no question about it,” says ,bird banding program manager at Powdermill.Measurements also revealed that the bird’s right wing was slightly longerthan the left, typical of the difference between male and female grosbeaks.While gynandromorphy simply means that an animal has both female and malecharacteristics, bilateral gynandromorphs often appear more dramaticallydifferent because those characteristics are separated down the middle oftheir body; the separation may be internal as well as external. And bilateralgynandromorphy is different from hermaphrodism, in which an organism hasboth male and female reproductive organs but may appear on the outsideto be either male or female.Although hermaphrodism is natural among many creatures, such earthwormsand snails, gynandromorphy is rare and, in birds, seems to occur .(.)In fact, since Powdermill began keeping records nearly six decades ago,Lindsay says, only five of roughly 800,000 captured birds have been documentedas likely gynandromorphs. The only other bird with bilateral gynandromorphyLindsay says she’s seen during the past 15 years was also a rose-breastedgrosbeak.“I think this time around I have more knowledge about just how rare thisis,” she says. “Just watching everyone else react—it was like pure joy.”“That bird is quite famous,” says ,a wildlife biologist at the Patuxent Wildlife Research Center’s Bird BandingLaboratory, in Maryland, a branch of the U.S. Geological Survey that servesas the central clearinghouse for data from bird banding operations acrossthe country.Looking back at all the records for the past 15 years, the odds of discoveringa gynandromorph in a bird-banding operation seem to be “almost exactlyone in a million,” Bystrak said in an email.But there’s a caveat to those long odds. Not all bird species have malesand females with noticeably different plumage, Lindsay says. More gynandromorphslikely are flying around out there than we realize.Bird collections in museums also shed light on the phenomenon. Over hiscareer, ,collection manager for the Section of Birds at Carnegie Museum of NaturalHistory, in Pittsburgh, Pennsylvania, has prepared some 16,000 birds forthe museum’s collections. That entails drying and preserving the birdsand taking notes on each specimen’s physical appearance, outside and inside,including its reproductive organs.Among the museum’s more than 27,000 specimens, Rogers found records foronly four gynandromorphs—three of them birds of species that have no colordifferences between males and females.“The one-in-a-million figure would only be for birds that show distinctdifferences,” Rogers says. “Cardinals, grosbeaks, and the like.”If you add in all the gynandromorphs that are hiding in plain sight, theodds go up to around 146 in a million.Gynandromorphs make headlines when they’re discovered, such as a from2019 and the foundearlier this year, but the phenomenon is difficult to study.Bystrak says he can find no record of a gynandromorph ever being re-capturedby a banding operation, so it’s unclear, for example, if the color differencespersist after the birds molt.There’s also the question as to what sort of future the grosbeak mighthave. Female birds, like humans, have two ovaries, but only the left oneis functional in songbirds. Since the grosbeak’s left side seems to befemale, Lindsay says it’s possible that the bird could reproduce—thoughit would also have to behave like a female to attract a mate.Not much is known about the behavior of gynandromorphs, but ,scientists were able to observe a northern cardinal in Illinois with bilateralgynandromorphy and noted that it seemed to survive into adulthood withoutdifficulties. Yet the cardinal never seemed to perform any songs or vocalizations,nor was it seen with a mate.In the end, we may never know what becomes of the grosbeak, a migratorybird. It was released the day it was caught and could be as far away asSouth America by now.You are leaving nationalgeographic.com. Different terms of use will apply.Copyright © 1996-2015 National Geographic Society.Copyright © 2015-2020 National Geographic Partners, LLC. All rights reserved

October 9, 2020Researchers with a team monitoring bird populations at Powdermill NatureReserve, in Rector, Pennsylvania, netted a surprise on September 24: arose-breasted grosbeak with bizarre coloring. It had the bright scarletfeathers of a male grosbeak on one side of its body and the canary yellowplumage of a female on the other.When they saw the robin-size songbird’s split coloring, it was immediatelyclear that the grosbeak was what scientists call a bilateral gynandromorph—ananimal that appears half male and half female.“There was no question about it,” says ,bird banding program...

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Half-female, half-male rose-breasted grosbeak found in Pennsylvania

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