For these birds, there is documented evidence of homosexual behavior in one or more of the following kinds: sex, courtship, affection, pair bonding, or parenting, as noted in researcher and author Bruce Bagemihl's 1999 book Biological Exuberance: Animal Homosexuality and Natural Diversity.(This is a dynamic list and may never be able to satisfy particular standards for completeness. You can help by adding missing items with reliable sources.) This list is part of a larger list of animals displaying homosexual behavior including mammals, insects, fish etc.