Rose-breasted Grosbeak: A bird which is both male and female
The Rose-breasted Grosbeak derives its name from the male of the species who have a ruby-red triangular marking on a white chest and dark black wings with pink wing pits.
Biologists have found a rare Rose-breasted Grosbeak, a bird with both female and male plumage colours, in the United States’ Pennsylvania. The Rose-breasted Grosbeak gynandromorph was caught by biologists from Powdermill Nature Reserve of the Carnegie Museum of Natural History’s environmental research centre in Rector, PA.
The Rose-breasted Grosbeak derives its name from the male of the species who have a ruby-red triangular marking on a white chest and dark black wings with pink wing pits. The females are much less showy, with no patches on its beige body, brown wings and yellow wing pits. Rose-breasted grosbeaks are sexually dimorphic, meaning they have both males and females have different colour plumage.
Researchers at Powdermill Nature Reserve made the extraordinary find on September 24. While catching and banding birds for the Avian Research Center, the team came across the Rose-breasted Grosbeak. This grosbeak observed at the reserve was split right down the middle - pink on the right side, yellow on the left.
Researchers said the condition is called bilateral gynandromorphism, means the bird is both male and female, with one ovary and one testis. This occurs when two sperm fertilize an egg that has two nuclei instead of one, which results in the egg to develop a chromosome from each sex.
The museum reports that in its 64 years of bird banding, the Avian Research Center has spotted less than 10 bilateral gynandromorphs. Since these birds have left functional ovaries, they could potentially lay eggs. However, it’s survival may depend on whether it makes male mating calls and risk getting attacked by other competitor males in the future.
“The entire banding team was very excited to see such a rarity up close, and are riding the high of this once-in-a-lifetime experience,” Annie Lindsay, the bird banding program manager, said in a press release.
What is a gynandromorph?
A gynandromorph is an organism that has both male and female characteristics - or, a male-female chimaera. It is often seen in insects, though gynandromorphic birds, snakes, lobsters and other animals have been observed, too, Lindsay said.
The extremely rare phenomenon occurs when two sperm fertilize an egg that has two nuclei instead of one. The egg can develop male sex chromosomes on one side and female on the other, leading to a bird with testis and other male characteristics on one half of its body and an ovary and other female characteristics on the other.
Gynandromorphs are not all that uncommon in the wild, though the colouration or markings of some species make the results more striking than others.