Examples of masculinized female pintails Anas acuta

Abstract

A presumed old female pintail Anas acuta with masculinized plumage pattern is here reported with its photo taken by Mr. Akio Sasagawa at Shinobazu pond, Ueno Zoo, Tokyo, early February, 1974. It has rough flank markings and elongated central tail feathess.
Another example of different plumage pattern also found at the same pond, photographed a 10 February 1976, by Mr. Kazue Nakamura is added.
Kuroda (1929, '39) had reported another old record of the pintail and a female Mandarin duck Aix galericulata was masculinized when molted after long kept in author's aviary.