Colombia is a fowl watcher’s paradise. Its stunningly various ecosystems — which embrace mountain ranges, mangrove swamps, Caribbean seashores and Amazonian rainforests — are house to extra avian species than some other nation on Earth.
So when Hamish Spencer, an evolutionary biologist on the College of Otago in New Zealand, booked a bird-watching trip in Colombia, he hoped to identify some fascinating and weird creatures.
He obtained greater than he bargained for. Throughout one outing, in early January 2023, the proprietor of an area farm drew his consideration to a inexperienced honeycreeper, a small songbird that’s frequent in forests starting from southern Mexico to Brazil.
However this specific inexperienced honeycreeper had extremely uncommon plumage. The left facet of its physique was coated in shimmering spring-green feathers, the traditional coloring for females. Its proper facet, nonetheless, was iridescent blue, the telltale marker of a male. The fowl gave the impression to be a bilateral gynandromorph: feminine on one facet and male on the opposite.
“It was simply unbelievable,” Dr. Spencer mentioned. “We had been fortunate to see it.”
Gynandromorphism has been documented in quite a lot of birds, in addition to bugs, crustaceans and different organisms. However it’s a comparatively uncommon and poorly understood phenomenon. The fowl Dr. Spencer noticed in Colombia is just the second identified case of bilateral gynandromorphism in a inexperienced honeycreeper — and the primary documented within the wild. (The one earlier instance was reported greater than a century in the past and was primarily based on a museum specimen, Dr. Spencer mentioned. That fowl displayed the alternative sample, with feminine plumage on the appropriate and male plumage on the left.)
It isn’t totally clear how the situation comes about, however one main idea is that it outcomes from an error in the course of the manufacturing of egg cells in feminine birds. Feminine birds have two completely different intercourse chromosomes, designated W and Z, whereas males have two Z chromosomes. An error throughout egg cell manufacturing may lead to two fused or incompletely separated cells, one with a W chromosome and one with a Z chromosome.
If these fused cells are fertilized by two completely different sperm, every of which carries a Z chromosome, the end result could be a fowl with the WZ chromosomes of a feminine in some cells and the ZZ chromosomes of a male in others. “And so that you get a fowl that’s half and half,” Dr. Spencer mentioned.
John Murillo, an novice ornithologist who owns a small farm and nature reserve in Colombia, first noticed the gynandromorphic honeycreeper in October 2021. It grew to become a daily customer to the farm’s fowl feeding station, which was stocked with recent fruit and sugar water. When Dr. Spencer and his bird-watching tour arrived on the farm greater than a yr later, Mr. Murillo identified the weird fowl and shared some pictures he had snapped of it.
“They’re one of the best pictures of a wild gynandromorphic fowl that I’ve ever seen,” Dr. Spencer mentioned. “I believed, The world must see these.”
The pictures had been included in a paper that Dr. Spencer and a number of other different scientists wrote concerning the uncommon honeycreeper, which was printed in The Journal of Area Ornithology in December. (Mr. Murillo was one of many authors.)
The fowl’s inside traits stay a thriller. In some, however not all, beforehand studied instances, gynandromorphic birds have had inside intercourse organs that matched their exterior plumage, with an ovary on one facet and a testis on the opposite. Previous observations recommend that some gynandromorphic birds can efficiently courtroom mates and reproduce.
However this specific inexperienced honeycreeper was by no means noticed partaking in any courtship or mating habits. It tended to keep away from different inexperienced honeycreepers and sometimes hung again from the feeding station till different birds had departed. “The fowl was inclined to be a little bit of a loner,” Dr. Spencer mentioned.
Nonetheless, it appeared to stay round, visiting the feeding station repeatedly over a interval of almost two years. “This fowl was round for a very long time,” Dr. Spencer mentioned. “It wasn’t at any type of apparent drawback, besides probably to find a mate.”