Observations on a presumed bilateral gynandromorph Black Redstart Phoenicurus ochruros paired with a male

Abstract

A supposed bilateral gynandromorph Black Redstart Phoenicurus ochruros in northwestern Switzerland formed a pair with a phenotypically classical male, but apparently was not breeding. The bird was documented before and after moult, when all replaced feathers were again of the same sex type. It was also recorded singing, the song being typical for the species. This is the second recorded case of a bilateral gynandromorph Black Redstart, one of only a handful cases where wild bilateral gynandromorph birds have been observed throughout the breeding season, and the first unequivocal documentation of a presumed bilateral gynandromorph bird forming a stable pair with a typical male.