Biological Exuberance: Animal Homosexuality and Natural Diversity

Mallards also sometimes form trio-bonds, either one male with two females (2–4 percent of all heterosexual bonds) or, more commonly, two males with one female (3–6 percent of all bonds). Paired males sometimes switch mates during the breeding season as well, and at least 9 percent of all heterosexual couples divorce between breeding seasons. Overall, long-term male-female pair-bonds (lasting two or more seasons) are rare in this species. Mallard mothers can be extremely aggressive in defense of their young, even killing other youngsters that stray from their own broods. In some populations the greatest cause of mortality among ducklings is attacks from other mothers. Occasionally, however, two broods join together and are defended by a single mother for short periods.

Other Species

Homosexual pairs also form among male Wood Ducks (Aix sponsa) that are raised together; such pairs are lifelong, and the two males may even search for nesting sites together each year. Female Chiloe Wigeons (Anas sibilatrix) have also been known to pair together in captivity; the partners remain bonded for many years and each lays eggs in their nest.

Sources

*asterisked references discuss homosexuality/transgender

Bailey, R. O., N. R. Seymour, and G. R. Stewart (1978) “Rape Behavior in Blue-winged Teal.” Auk 95:188-90.

Barash, D. P. (1977) “Sociobiology of Rape in Mallards (Anas platyrhynchos): Responses of the Mated Male.” Science 197:788–89.

Boos, J. D., T. D. Nudds, and K. Sjoberg (1989) “Posthatch Brood Amalgamation by Mallards.” Wilson Bulletin 101:503–5.

*Bossema, I., and E. Roemers (1985) “Mating Strategy, Including Mate Choice, in Mallards.” Ardea 73:147–57.

Cheng, K. M., J. T. Burns, and F. McKinney (1983) “Forced Copulation in Captive Mallards. III. Sperm Competition.” Auk 100:302-10.

Evarts, S., and C. J. Williams (1987) “Multiple Paternity in a Wild Population of Mallards.” Auk 104:597–602.

*Geh, G. (1987) “Schein-Kopula bei Weibchen der Stockente Anas platyrhynchos [Pseudo-Copulation of Female Mallard Ducks].” Anzeiger der Ornithologischen Gesellschaft in Bayern 26:131–32.

*Hochbaum, H. A. (1944) The Canvasback on a Prairie Marsh. Washington, D.C.: American Wildlife Institute.

Huxley, J. S. (1912) “A ‘Disharmony’ in the Reproductive Habits of the Wild Duck (Anas boschas L.).” Biologisches Centralblatt 32:621–23.

*Lebret, T. (1961) “The Pair Formation in the Annual Cycle of the Mallard, Anas platyrhynchos L.” Ardea 49:97–157.

*Lorenz, K. (1991) Here Am I—Where Are You? The Behavior of the Greylag Goose. New York: Harcourt Brace Jovanovich.

*———(1935) “Der Kumpan in der Umwelt des Vogels.” Journal fur Ornithologie 83:10–213, 289–413. Reprinted as “Companions as Factors in the Bird’s Environment.” In K. Lorenz (1970), Studies in Animal and Human Behavior, vol. 1, pp. 101-258. Cambridge, Mass.: Harvard University Press.

Losito, M. P., and G. A. Baldassarre (1996) “Pair-bond Dissolution in Mallards.” Auk 113:692-95.

McKinney, F., S. R. Derrickson, and P. Minneau (1983) “Forced Copulation in Waterfowl.” Behavior 86:250–94.

Mjelstad, H., and M. S?tersdal (1990) “Reforming of Resident Mallard Pairs Anas platyrhynchos, Rule Rather Than Exception?” Wildfowl 41:150–51.

Raitasuo, K. (1964) “Social Behavior of the Mallard, Anas platyrhynchos, in the Course of the Annual Cycle.” Papers on Game Research (Helsinki) 24:1-72.

*Ramsay, A. O. (1956) “Seasonal Patterns in the Epigamic Displays of Some Surface-Feeding Ducks.” Wilson Bulletin 68:275–81.

*Schutz, F. (1965) “Homosexualitat und Pragung: Eine experimentelle Untersuchung an Enten [Homosexuality and Developmental Imprinting: An Experimental Investigation of Ducks].” Psychologische Forschung 28:439–63.

*Titman, R. D., and J. K. Lowther (1975) “The Breeding Behavior of a Crowded Population of Mallards.” Canadian Journal of Zoology 53:1270–83.

Weston, M. (1988) “Unusual Behavior in Mallards.” Vogeljaar 36:259.

Williams, D. M. (1983) “Mate Choice in the Mallard.” In P. Bateson, ed., Mate Choice, pp. 33–50. Cambridge: Cambridge University Press.

LESSER SCAUP DUCK

IDENTIFICATION: A broad-billed duck with a purplish black head and breast and white underparts in males, and a dark head and brownish plumage in females. DISTRIBUTION: Northern and central North America; winters in southern United States and Mexico. HABITAT: Lakes, marshes, lagoons. STUDY AREAS: Lake Manitoba (Delta Marsh) and near Erickson, Manitoba; Cariboo region of British Columbia, Canada, including Watson and 150 Mile Lakes.

AUSTRALIAN SHELDUCK

IDENTIFICATION: Cinnamon breast, dark green head and back, and white collar; adult females have white eye and bill rings. DISTRIBUTION: Southern Australia, Tasmania. HABITAT: Marshes, lakes, lagoons. STUDY AREA: Rottnest Island, Western Australia.

MUSK DUCK

IDENTIFICATION: A large, grayish duck with a prominent lobe hanging from the lower bill, and a spike-fan tail. DISTRIBUTION: Southern Australia, Tasmania. HABITAT: Swamps, lakes, other wetlands. STUDY AREA: Kangaroo Lake, Victoria, Australia.

Social Organization

Lesser Scaup Ducks are highly social, gathering into large waterborne flocks or “rafts” that may number in the tens of thousands. They form pair-bonds during the mating season, but males typically leave their mates following egg-laying (see below) and join large all-male groups. Australian Shelducks also form mated pairs during the breeding season (both parents care for the young) but otherwise associate in flocks. Musk Ducks are largely solitary except during the mating season; adult males are territorial, and they are probably polygamous or promiscuous (copulating with more than one female).

Description

Behavioral Expression: Male Lesser Scaup Ducks occasionally try to copulate with one another; drakes who participate in such homosexual activity are usually unpaired birds. While same-sex mounting does not occur among females, coparenting does. In this species, males usually abandon their female mates shortly after incubation of the eggs begins. Most females take care of their young entirely on their own as single parents, but sometimes two females join together and help each other raise their families. Accompanying their combined broods of 20 or more ducklings, the two females cooperate in all parental duties, including coordinated defense of the youngsters. If a predator or intruder approaches, one female distracts it by boldly approaching and feigning an injury, while her partner stealthily leads all of the ducklings away to safety. As their offspring get older, however, female coparents show less of this “distraction” behavior; at the approach of a