Transvestite raptor
Male marsh harriers are mostly grey, with yellow eyes, while females are brown with white heads and shoulders, and brown eyes. Females are also about 30 per cent bigger than males.
Not all males obey the gender rules, though. Up to 40 per cent of them have mainly brown feathers with no greys at all, though they do still have the yellow eyes that mark them as male, and are no bigger than expected for their gender. These female-like males acquire their unusual colour in their second year, and keep it for the rest of their lives.