to draw comparisons between humans and other apes because our behaviour is so much more complex than any other species. For instance, some species of fish change sex depending upon needs of the local populations. It's okay for grey whales or bonobo apes to rub their willies together but they don't appear to suffer from the psychological impedimentia that humans have.

However, it appears in the bird world so far it has only noted two species where males pretend to be females, developing the plumage of the female and living apparently as females i.e. not attacking other males. These are the Marsh Harrier and the Ruff.

http://www.paneuropeannetworks.com/detail/environment/male-m...