What birds have complex convoluted genitals?
Ducks and geese have a very complex structure of the genitalia. Male phallus forming a spiral shape and can reach a length of the size of the entire body.
A similar spiral form characteristic of the ovary and female of these birds, and it is so sophisticated, the harder penis drake. In some species of ducks and geese, male and female form a permanent pair, but the females are at risk of being "raped" by other males. In order not to withdraw from strangers offspring, ovarian cavity of the birds may have some false pockets, where blocks unwanted sperm.