In Rector, Pennsylvania., researchers have spotted 1 Rare bird.
This rose-breasted grosbeak features a pink breast spot & a pink “wing pit” and black feathers on its right wing — telltale shades-of-males. But on its left side, the songbird displays yellow & brown plumage, hues typical of females.
Annie Lindsay had been out capturing & banding birds with identification tags together with her colleagues at Powdermill Nature Reserve in Rector on Sep 24 when a teammate hailed her on her walkie-talkie to alert her of the bird’s discovery. Lindsay, who is banding program manager at Powdermill, immediately knew what she was looking at: a half-male, half-female creature referred to as a gynandromorph.
“It was spectacular. This bird is in its nonbreeding, so in spring when it’s in its breeding plumage, it’s getting to be even more starkly male, female,” Lindsay says. The bird’s colors will become even more vibrant, and “the line between the male & female side will-be even’ more obvious.”
Such birds are rare. Lindsay has seen just one other similar, but less striking, bird 15 years ago, she says.
Gynandromorphs are found in many species of birds, insects & crustaceans like crabs & lobsters. This bird is probably going the results of an unusual event when 2 sperm fertilize an egg that has 2 nuclei rather than one. The egg can then develop male sex chromosomes on one side & female sex chromosomes on the opposite, ultimately resulting in a bird with a testis & other male characteristics on one half its body & an ovary & other female qualities on the opposite half.
Unlike hermaphrodites, which even have genitals of both sexes, gynandromorphs are completely male on one side of the body & female on the opposite .
Scientists don’t know if these birds behave more like males or females, or if they will reproduce. UCLA biologist Arthur Arnold studied one gynandromorph zebra finch that used a male song & behavior to attract females. But there need’ to be more studies on whether behavior associated with one sex is more dominant than the other across gynandromorphs, he says. Such research is hard , however, because the creatures are so rare.
In 64 years of bird banding, Powdermill’s Avian Research Centre has recorded fewer than 10 such birds. After marveling over their new find in field, Lindsay and her colleagues took the rose-breasted grosbeak to the laboratory, measured its wing span & plucked out four feathers to get its DNA for future studies. The team later took photographs & TikTok videos with the small feathery guest before letting it fly its way.