(Under Construction. For now, this page is no more than an unstructured, expanding listing of possibly related posts. By all means follow the links that are included, but these are as yet nowhere complete. Italicized links are not yet working).
It is often claimed that homosexuality is “unnatural”, and is not found in the animal kingdom. This belief is entirely false. The empirical evidence from the field is that same sex genital activity, and also non-procreative heterosexual activity, is widespread through all branches of the animal kingdom. In some species, and for some individuals in others, same sex mating is even more common than the opposite sex variety. Even joint parenting by same sex couples has been widely reported (especially for birds), and is often more successful than opposite sex parenting.
These pages elaborate the evidence, with links to posts on specific animals
Confirmed: God is Slightly Gay – Homosexuality in the Animal Kingdom
Some Specific Examples
Same Sex Parenting
Other Non-Procreative Animal Sex