In the Don Miguel Demonstrative Nature Reserve, located near Manizales, in Colombia, amateur ornithologist John Murillo made a surprising discovery: a green honeyeater (Chlorophanes spiza) with unique plumage. This specimen presented an extraordinary phenomenon known as bilateral gynandromorphy, in which one side of the organism shows male characteristics and the other, female characteristics.
This green honeyeater exhibited green plumage on the left side, typical of females of the species, and blue plumage on the right side, characteristic of males. Bilateral gynandromorphy is an extremely rare condition in birds, and this finding is the second example recorded in the species in more than 100 years.
Evolutionary geneticist Hamish Spencer, professor in the Department of Zoology at the University of Otago, New Zealand, described this phenomenon as “extremely exciting” and highlighted the rarity of finding a gynandromorph in birds. These types of conditions are known in several groups of animals, especially those that show pronounced sexual dimorphism.
Bilateral gynandromorphy arises from an error during cell division in the female to produce an egg, followed by double fertilization by two sperm. Although this phenomenon is more easily detectable in sexually dimorphic species, such as birds, its occurrence is exceptional.
This particular case of bilateral gynandromorphy was observed for at least 21 months in the Don Miguel Demonstrative Natural Reserve. Despite its uniqueness, the green honeyeater behaved similarly to other individuals of its species, showing territoriality and avoiding contact with others of its species.
The discovery of this strange half-male, half-female bird provides valuable information about sex determination and sexual behavior in birds, according to experts. Its presence in the Don Miguel Demonstrative Natural Reserve becomes a unique testimony of the diversity and complexity of nature.
