Liputan6.com, Jakarta A green honeycreeper was spotted in a nature reserve in Colombia with green (female) feathers on one side and blue (male) on the other. Although it sounds like a joke or something I might have caused, this condition is known as bilateral gynandromorphy. This is the second documented case of bilateral gynandromorphy in this species, as quoted from the Discover Wildlife page, Thursday (9/11/2025).
Bilateral gynandromorphism is believed to occur when a female bird's egg develops two nuclei fertilized by two different sperm, known as double fertilization.
Advertisement
The resulting offspring has female cells on one side of its body and male cells on the other. In addition to its split plumage, the bird has ovaries on the female side and testes on the male side. It can theoretically mate with both.
Bilateral gynandromorphy is much easier to find in sexually dimorphic species, where males and females look different. The phenomenon was first seen in October 2021, and sightings continued until June 2023. The bird was spotted at a Reserva Natural Demostrativa Don Miguel feeding station in Colombia.
Amateur ornithologist John Murillo spotted the bird and showed it to visiting observers, including Hamish Spencer from the Department of Zoology at the University of Otago, New Zealand.
"It was a joy to see this bird," says Spencer, co-author of the paper published in the Journal of Field Ornithology in December 2023.
"Most bird lovers tend never to see a gynandromorph in their lifetime, so I feel very lucky to have seen John's discovery."