Biological Exuberance: Animal Homosexuality and Natural Diversity

Adolescent male Lyrebirds also sometimes mount one another as well as particpate in homosexual courtship displays. Courtship between younger males is usually mutual, with both birds singing and displaying to one another. Occasionally an adult and an adolescent male also engage in mutual display, and adult females (in captivity) have been observed performing a similar courtship display to each other. Typically, the two adolescent males circle around each other on a display mound, tails raised in a fan shape with their feathers intermingled and beaks nearly touching while performing a vocal duet. One male may also perform a full-face or invitation display, and his partner sometimes runs underneath his outstretched tail the way a female does during heterosexual courtship. Sometimes the two males engage in what appears to be a form of COURTSHIP-FEEDING: in response to begging from his partner, one male regurgitates a worm or other food item as an offering to the other, who promptly eats it. This behavior appears to be unique to homosexual courtships. Two younger males often form a “companionship”: in addition to courting each other, they follow one another, feed together (even digging in the same hole for food items), roost next to each other, and share bathing pools. These male pair-bonds usually last for only a few days, and adolescent males often form multiple serial attachments of this sort.

Two younger male Superb Lyrebirds performing a mutual courtship display

Frequency: Homosexual courtship occurs fairly often in Superb Lyrebirds. Adult males approach groups of adolescent males approximately once every three days during the breeding season and roughly once every day and a half outside the breeding season, and 93 percent of these encounters include courtship. In comparison, heterosexual encounters occur about four times as often as homosexual encounters during the breeding season, and about twice as often outside the breeding season. Adult males associate with adolescent males (in groups or singly) more than half of the time they are away from their display mounds. Same-sex mounting occurs less frequently than courtship interactions between males.

Orientation: Most adult males are functionally bisexual, courting and mounting both females and younger males. Adolescent males appear to be more exclusively homosexual: most individuals form same-sex companionships and engage in homosexual courtship (and sometimes mounting) for several years prior to mating heterosexually. Some females probably have a bisexual potential that manifests itself in the absence of males (for example, in captivity).

Nonreproductive and Alternative Heterosexualities

Male and female Superb Lyrebirds lead largely separate lives. Other than brief encounters during the breeding season for courtship and copulation, the two sexes rarely interact: only about 8—10 percent of all Lyrebird sightings are of males and females together. Because males do not contribute at all to parenting, incubation and chick-raising often become burdensome for females—and by extension, potentially harmful for the eggs and/or chicks. During the early stages of incubation, females regularly leave their eggs unattended during the day for up to seven hours at a time to feed, causing the egg temperature to drop dramatically. Overall, females are relatively “inattentive” parents, incubating their eggs for only about 27—45 percent of the available daylight hours; this is significantly less than in other perching birds, who generally spend 60—80 percent. Because the eggs are laid and incubated during the coldest months of winter, they are consequently exposed to dangerously low (sometimes even sub-freezing) temperatures that generally slow embryonic development. After hatching, nestlings occasionally die from overexposure when their mother has been away from the nest for too long.

Sources

*asterisked references discuss homosexuality/transgender

Kenyon, R. F. (1972) “Polygyny Among Superb Lyrebirds in Sherbrooke Forest Park, Kallista, Victoria.” Emu 72:70—76.

Lill, A. (1986) “Time-Energy Budgets During Reproduction and the Evolution of Single Parenting in the Superb Lyrebird.” Australian Journal of Zoology 34:351—71.

*———(1979a) “An Assessment of Male Parental Investment and Pair Bonding in the Polygamous Superb Lyrebird.” Auk 96:489—98.

———(1979b) “Nest Inattentiveness and Its Influence on Development of the Young in the Superb Lyrebird.” Condor 81:225—31.

Reilly, P. (1988) The Lyrebird: A Natural History. Kensington, Australia: New South Wales University Press.

*Smith, L. H. (1996-97) Personal communication.

*———(1988) The Life of the Lyrebird. Richmond, Australia: William Heinemann.