The first case of bilateral gynandromorphic plumage type in the bearded reedling Panurus biarmicus

Abstract

Bilateral gynandromorphism is a condition in which an individual has both male and female phenotypes distributed symmetrically on the body. We describe the first case of a likely gynandromorphic bearded tit, which was trapped in Poland. The bird had a black moustache and grey-blue plumage on the right side of the head, which is typical for males, and lacked this plumage coloration on the left side, which is typical of females. The entire bill was brown, consistent with a typical female, while the undertail coverts were buff with randomly distributed black spots, which represents a mixture feature of both sexes. The observation is discussed in light of earlier cases of gynandromorphic birds.