Many species of birds are sexually dimorphic in the color pattern of their feathers. Just recently, a striking and extremely rare half-female, half-male bird was spotted by a zoologist in Colombia.
Dual-Gender Honeycreeper
University of Otago Professor Hamish Spencer was on holiday in Colombia when amateur ornithologist John Murillo pointed out a wild green honeycreeper (Chlorophanes spiza). What makes this bird remarkable is its distinct half-green and half-blue plumage.
This rare discovery is only the second recorded example of gynandromorphism in honeycreepers in over 100 years. Images of the bird make the discovery more significant since they are considered the best wild bilateral gynandromorphic birds of any species.
The green honeycreeper is a small tanager species belonging to the bird family Thraupidae. It is common and conspicuous from southern Mexico to southeastern Brazil. This bird mainly feeds on fruits, insects, and nectar and often frequents bird feeders that supply fruit.
The green honeycreeper's plumage is strikingly sexually dimorphic - females are grass green and slightly paler underneath. At the same time, males are aqua blue with a black chin, mask, and hood.
Bill color is also sexually dimorphic in this bird species. Males possess a bright yellow mandible and lower maxilla with a black culmen. Females, on the other hand, have a dull yellow mandible and a black maxilla. Juvenile green honeycreepers mostly resemble the females.
There appears to be no significant difference between males and females regarding body mass. Although males, on average, have longer wings and tails than females, there is considerable variation within each kind and much overlap.
The bilateral gynandromorphy phenomenon was observed in green honeycreepers at a feeding station in Villamaría in Caldas, Colombia, between October 2021 and June 2023. Professor Spencer hopes this discovery will inspire people to value exceptions as they reveal something interesting about nature.
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What is Bilateral Gynandromorphy?
Bilateral gynandromorphy is a condition where one side of an organism exhibits male characteristics while the other exhibits female features. This condition is observed in many animal groups, especially in sexually dimorphic organisms, like some varieties of crustaceans, snakes, insects, and birds.
This phenomenon is thought to arise in birds due to an error during egg meiosis, where there is subsequent double fertilization by separate sperm cells. As a result, one side of the bird has heterogametic female cells (ZW) female cells while the other has homogametic (ZZ) male cells. To gain more insight into sex determination and sexual behavior in birds, scientists examine the internal structure of the brain and other organs of gynandromorphs.
According to biologist Janice L. Krumm, gynandromorphy can manifest in several forms. In the bilateral version, the male/female division is shown on the right and left sides of the body. It can also be axial, where the two characteristics are separated in front and back, or mosaic, where the animal is a patchwork of male and female.
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