Black Swans
An estimated one-quarter of all black swans pairings are homosexual and they steal nests, or form temporary threesomes with females to obtain eggs, driving away the female after she lays the eggs.
Penguin
Male penguin couples have been documented to mate for life, build nests together, and to use a stone as a surrogate egg in nesting and brooding. In 2004, the Central Park Zoo in the United States replaced one male couple's stone with a fertilized egg, which the couple then raised as their own offspring.
Lions
Both male and female lions have been seen to interact homosexually. Male lions pair-bond for a number of days and initiate homosexual activity with affectionate nuzzling and caressing, leading to mounting and thrusting.
