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.
According to Bagemihl, animal sexual behavior takes many different forms, even within the same species and the motivations for and implications of their behaviors have yet to be fully understood. Bagemihl's research shows that homosexual behavior, not necessarily sex, has been documented in about 500 species as of 1999, ranging from primates to gut worms.[2][3]Homosexuality in animals is seen as controversial by social conservatives because it asserts the naturalness of homosexuality in humans, while others counter that it has no implications and is nonsensical to equate animal behavior to morality.[4][5] Animal preference and motivation is always inferred from behavior. Thus homosexual behavior has been given a number of terms over the years. The correct usage of the term homosexual is that an animal exhibits homosexual behavior, however this article conforms to the usage by modern research[6][7][8][9] applying the term homosexuality to all sexual behavior (copulation, genital stimulation, mating games and sexual display behavior) between animals of the same sex.
Chilean flamingoes eating, drinking, and preening in St. Petersburg, Florida; flamingos (as well as penguins and other species) sometimes form committed same-sex relationships that can involve sex, traveling and living together, and raising young together.[10]
The black swan, Cygnus atratus is a large waterbird which breeds mainly in the southeast and southwest regions of Australia. 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.[13][14]
Harrold, Max (February 16, 1999). "Creature Comforts". The Advocate. No. 779. pp. 61–62. Retrieved March 10, 2018. In his news book, Biological Exuberance: Animal Homosexuality and Natural Diversity ... author Bruce Bagemihl portrays an animal kingdom that embraces a whole spectrum of sexual orientations ... [and] paints a complex mosaic that resembles humanity ... At 751 pages and with photos and documentation of homosexual behaviour in more than 450 species of mammals, birds, repties, and insects, Biological Exuberance brings the dusty facts to light as Bagemihl deconstructs the all-heterosexual Noah's Ark we've been sold.
Liggett, Dave; Columbus Zoo and Aquarium staff. "African Forest: Bonobo". Columbus Zoo and Aquarium. Archived from the original on June 2, 2002. Retrieved November 14, 2011. ...frequent sex (including male-to-male and female-to-female) characterize bonobo society.
Roselli, Charles E., Kay Larkin, John A. Resko, John N. Stellflug and Fred Stormshak (2004). "The Volume of a Sexually Dimorphic Nucleus in the Ovine Medial Preoptic Area/Anterior Hypothalamus Varies with Sexual Partner Preference". Endocrinology, Department of Physiology and Pharmacology, Oregon Health & Science University (C.E.R., K.L., J.A.R.), Portland, Oregon; Department of Animal Sciences, Oregon State University (F.S.), Corvallis, Oregon; and Agricultural Research Service, United States Sheep Experiment Station (J.N.S.), Dubois, Idaho, Vol. 145, No. 2. Retrieved on 10 September 2007.
Schaller, G. B. (1972). The Serengeti Lion; University of Chicago Press.
Smith, Dinitia (7 February 2004). "Love That Dare Not Squeak Its Name"New York Times. Retrieved on 10 September 2007. Reprinted as "Central Park Zoo's Gay Penguins Ignite Debate", San Francisco Chronicle.