In the forests of Pennsylvania, biologists have managed to catch an incredibly rare bird that is genetically half-male, half-female, showcasing the visual characteristics of both genders.
The Big Day
Researchers at the Carnegie Museum of Natural History caught a unique bird on September 24th in the Powder Mill Wildlife Sanctuary in Pennsylvania. The unusual bird belongs to a species known as the Rose-breasted Grosbeak or as it is known in the Latin term Pheucticus Ludovicianus.
It is a large seed-eating member of the cardinal bird family found in eastern North America. The male of this species is known for its bright and colorful feathers, but this captured individual has particularly distinctive colored feathers that differ on each side of the body: the right side is pink and red as characteristic of the male bird and the left side is brown and orange that is the feature of a female bird. This is because the bird is a rare example of bilateral gynecomorphism, where the external appearance of the animal is divided through the middle of the body into two parts by both genders, as a result, this bird is half-male and half-female.
The whole team was very happy to have the opportunity to see such a rarity from so close. One team member described it as “seeing a unicorn,” and another compared it to the sense of an adrenaline rush when you see something so extraordinary. Although, the bilateral gynecomorphism is very unusual, it is a normal phenomenon. It might be said that it is a perfect example of an impressive genetic process that few people experience.
How Does This Phenomenon Occur?
First of all, the gender determination of birds is slightly different from the process that can determine the gender for human beings. There are usually 2 identical gender chromosomes (XX) in the cells of human females, and 2 unequal chromosomes (XY) in the cells of human males. For birds it is different, as a result, males have a double gender chromosome (ZZ) and females have one chromosome (ZW). Bilateral gynecomorphism is thought to occur for different reasons in different species, but in birds it occurs when an ovum randomly develops with two nuclei, one with a Z chromosome and the other with a W chromosome. If that ovum is fertilized by a cell with two Z chromosomes, the ovum develops with both ZZ (male) and ZW (female) chromosomes.
The team that discovered this bird is now wondering if it can breed successfully. Since such birds usually have only the left ovary functioning and the left side of this bird is a female, in theory an individual can breed with another male. However, it is likely that its unusual feathers may elicit a territorial response from other males, which would reduce its chances of successfully survive. Although the likelihood of gynecomorphism is exceptionally low, reciprocal gynecomorphism has been observed in many different animals. In 2019, the scientists also observed a northern cardinal (Cardinalis cardinalis) in Pennsylvania, whose gynecomorphism features were semi-brown, semi-red in color, as a result, these are the characteristics of both genders of the bird.