Biological Exuberance: Animal Homosexuality and Natural Diversity

In a detailed study of parental behavior by female pairs of Ring-billed Gulls, scientists found no significant differences in quality of care provided by homosexual as opposed to heterosexual parents. They concluded that there was not anything that male Ring-billed Gull parents provided that two females could not offer equally well.¹² This case is not exceptional: homosexual parents are generally as good at parenting as heterosexual ones. Examples of same-sex pairs successfully raising young have been documented in at least 20 species, and in a few cases, homosexual couples actually appear to have an advantage over heterosexual ones.¹³ Pairs of male Black Swans, for example, are often able to acquire the largest and best-quality territories for raising young because of their combined strength. Such fathers—dubbed “formidable” adversaries by one scientist—consequently tend to be more successful at raising offspring than most heterosexual pairs.¹⁴ And in many species in which single parenting is the rule (because there is no heterosexual pair-bonding), same-sex pairs provide a unique opportunity for young to be raised by two parents (e.g., Squirrel Monkeys, Grizzly Bears, Lesser Scaup Ducks). Moreover, in some Gulls, female pairs are consigned (for a variety of reasons) to less than optimal territories, yet they still successfully raise young: in many cases they compensate by investing more parental effort—and are more dutiful in caring for their chicks—than male-female pairs.¹⁵ There are exceptions, of course: some female pairs of Gulls, for instance, tend to lay smaller eggs and raise fewer chicks (although this is also true of heterosexual trios attending supernormal clutches), while same-sex parents in Jackdaws, Canada Geese, and Oystercatchers may experience parenting difficulties such as egg breakage or nonsynchronization of incubation duties. By and large, though, same-sex couples are competent and occasionally even superior parents.

Birds in homosexual pairs often build a nest together. Usually they construct a single nest the way most heterosexual pairs do, but other variations also occur: female Common Gulls and Jackdaws sometimes make “twin” or “joint” nests containing two cups in the same bowl, while male Greater Rheas and female Canada Geese may use “double” nests consisting of two adjacent or touching nests. Female Mute Swans occasionally construct two separate nests in which both birds lay eggs. Nests belonging to male couples in some species (e.g., Flamingos and Great Cormorants) are often impressive structures, exceeding the size of heterosexual nests because both males contribute equally to their construction (in heterosexual pairs of these species, usually only one sex builds the nest, or males and females make unequal contributions). Many same-sex pairs construct nests regardless of whether they lay fertile eggs. Male pairs of Mute Swans, Flamingos, Black-crowned Night Herons, and Great Cormorants, for example, usually build nests even though they never acquire eggs, and the male “parents” may even sit on the nests as if they contained eggs, while female pairs frequently build nests in which they lay supernormal clutches that are entirely infertile. Same-sex parents often share incubation duties, either taking turns sitting on their nest (the most common arrangement), or else incubating simultaneously on a single nest (female Red-backed Shrikes, male Emus) or side by side on a twin or double nest (female Jackdaws, male Greater Rheas).

In addition to parenting by homosexual couples, some animals raise young in alternative family arrangements, usually a group of several males or females living together. Gorilla babies, for example, grow up in mixed-sex, polygamous groups where their mothers may have lesbian interactions with each other, while Pukeko and Acorn Woodpeckers live and raise their young in communal breeding groups where many, if not all, group members engage in courtship and sexual activities with one another (both same-sex and opposite-sex). In such situations, individuals that engage in homosexual courtship or copulation activities may either reproduce directly because they also mate heterosexually (Pukeko), or they may assist members of their group in raising young without reproducing themselves (Acorn Woodpeckers).¹⁶ Other alternative family constellations include bisexual trios (mentioned above), homosexual trios (as in Grizzly Bears, Dwarf Cavies, Lesser Scaup Ducks, and Ring-billed Gulls) where three mothers jointly parent their offspring, and even quartets, in which four animals of the same (Grizzlies) or both sexes (Greylag Geese) are bonded to each other and all raise their young together.¹⁷