Why is this bird two-toned? It has the green feathers of a female honeycreeper on one side and a male’s blue feathers on the other. This type of split is called bilateral gynandromorphism (gyn-an-druh-MOR-fih-zuhm).
This rare condition occurs during reproduction. If a bird produces a fertilized egg with both male and female DNA inside, the chick will hatch with two-tone coloring. This is only the second green honeycreeper ever seen with this condition! It’s also seen in butterflies, snakes, and crustaceans.
Studying birds like this one helps scientists learn how they develop male and female traits. In nature, these unexpected changes “tell you something or suggest questions that you never would have thought about otherwise,” says Hamish Spencer, an evolutionary biologist at the University of Otago in New Zealand.