Biological Exuberance: Animal Homosexuality and Natural Diversity

*Schonfeld, M. (1985) “Beitrag zur Biologie der Schwane: ‘Mannchenpaar’ zwischen Graugans und Hock- erschwan [Contribution to the Biology of Swans: ‘Male Pairing’ Between a Greylag Goose and a Mute Swan].” Der Falke 32:208.

Sears, J. (1992) “Extra-Pair Copulation by Breeding Male Mute Swan.” British Birds 85:558–59.

*Whitaker, J. (1885) “Swans’ Nests.” The Zoologist 9:263–64.

Williams, M. (1981) “The Demography of New Zealand’s Cygnus atratus Population.” In G. V. T. Matthews and M. Smart, eds., Proceedings of the 2nd International Swan Symposium (Sapporo, Japan), pp. 147–61. Slimbridge: International Waterfowl Research Bureau.

MALLARD DUCK

IDENTIFICATION: A familiar duck with a blue wing patch, an iridescent green head and white collar in males, and brown, mottled plumage in females. DISTRIBUTION: Throughout the Northern Hemisphere; Australia and New Zealand. HABITAT: Wetlands. STUDY AREAS: J. Rulon Miller Wildlife Refuge, McDonogh, New Jersey; Haren and Middleburg, the Netherlands; Augsburg, Germany, and the Max-Planck Institute, Seewiesen, Germany; Delta Waterfowl Research Station, Lake Manitoba, Canada; subspecies A.p. platyrhynchos, the Common Mallard.

BLUE-WINGED TEAL

IDENTIFICATION: A grayish brown duck with a light blue upper-wing patch, tawny spotted underparts, and white, crescent-shaped facial stripes in males. DISTRIBUTION: Northern and central North America; winters in Central America and northern South America. HABITAT: Marshes, lakes, streams. STUDY AREA: Delta Waterfowl Research Station, Lake Manitoba, Canada.

Social Organization

Mallard Ducks and Blue-winged Teals are highly sociable birds, usually congregating in their own flocks of hundreds or (in Mallards) even thousands for most of the year. During the breeding season, they typically form monogamous pairs, although many variations exist. As in many other duck species, heterosexual pairs usually separate soon after incubation begins. Females then incubate the eggs and raise their families on their own.

Description

Behavioral Expression: Female Mallards sometimes mount and copulate with other females in the early fall, when ducks congregate in groups and begin to establish pair-bonds. Two females may engage in the PUMPING display, a prelude or invitation to mating in which the head is bobbed up and down so that the bill touches the water in a horizontal position. Following this, one female flattens her body on the water and extends her neck, allowing the other female to mount. While copulating, the mounting female may grab her partner’s neck feathers in her bill or gently peck at her head. After dismounting, she performs a concluding display (also shown by females in heterosexual interactions) in which she dips her head in the water and then shakes the drops down her back while beating her wings. Homosexual mountings occasionally occur later in the season between heterosexually paired females and single females.

Homosexual pair-bonds also occur in both male and female Mallards. As in heterosexual pairs, the two partners keep close company, swimming together as well as resting, preening, and feeding in perfect synchrony. Same-sex partners also “defend” their mate from the approach of other Mallards. Females use a special INCITING display for this, in which they trail their partner while looking back over their shoulder and making a trembling call. Overt sexual activity is not generally a feature of same-sex partnerships, however: drake pairs, for example, engage in mutual head pumping and feather ruffling (which are preludes to copulation) but neither partner mounts the other or invites his mate to mount him. Interestingly, though, some males in homosexual pairs have been observed attempting to rape or forcibly copulate with males outside their pair-bond (just the way drakes in heterosexual pairs often participate in nonmonogamous raping of females—see below). Among females, homosexual pair-bonds are more ephemeral, generally occurring only in the pre-and postbreeding seasons. Some drake pairs are also temporary, while others are long-lasting, persisting for years and possibly even for life.

A homosexual pair of male Mallard Ducks engaging in synchronized preening

A flock, or “club,” of homosexual Mallard drakes

Male Mallards that have been raised together also frequently develop homosexual bonds of great strength and longevity. When large numbers of such birds are present, they often form their own groups, known as CLUBS. They flock together for hours or even days at a time, excitedly running about and swimming together while quacking continuously. Sometimes a female associates herself with a drake pair to form a bisexual trio; although one or both males may mate with her, their homosexual bond remains primary. Less commonly, females that have been raised together may also form a pair-bond, jointly incubating a nest and coparenting any ducklings that may result from promiscuous matings with males.

Blue-winged Teal drakes will court each other in the absence of females, even competing and fighting with one another for the attentions of another male.

Frequency: Homosexual copulations and pairings between female Mallard Ducks occur sporadically and are most common during the fall. In one study, roughly a quarter of the days on which sexual activity was observed included same-sex mountings. The proportion of male homosexual pairs varies between populations, anywhere from 2–19 percent of all pairs.

Orientation: Several forms of bisexuality occur among Mallards: females may participate in homosexual copulations while paired with a male, and both sexes may form seasonal homosexual attachments prior to or following a period of heterosexual mating. Some males are probably more exclusively homosexual, forming ongoing same-sex bonds that last for many years. In addition, most males probably have a bisexual potential: when raised in all-male groups, Mallards usually form lifelong homosexual pairs, and re- pair with other males on being “widowed.” Nevertheless, even among males that have not been raised together, approximately 13–17 percent still participate in homosexual pairing for at least a portion of their lives. In Blue- winged Teals, homosexual behavior appears to be primarily a manifestation of a bisexual potential, since same-sex pairing or courtship have so far only been observed in males isolated from females.

Nonreproductive and Alternative Heterosexualities

Mallard pairs regularly engage in nonreproductive matings. For example, copulation is common during the five-to-seven months that heterosexual couples are together prior to the breeding season (when males are not producing sperm). Later in the breeding season, however, male-female relations are often marked by hostility, since forced copulation or rape is a common feature of opposite-sex interactions in both Mallards and Blue-winged Teals. Following egg-laying, male Mallards regularly abandon their female mates (who thus become “single parents”), congregate in all-male groups, and begin pursuing other females to try to forcibly mate with them. Rapes also occur between paired ducks in both species. As many as a 12–40 males may chase a single female in aerial or aquatic pursuit; drakes have even been known to grab and mount females underwater when they dive (attempting to escape), or to knock females to the ground in midflight. In some populations, as many as 7–10 percent of all females die each year as a result of drownings or other injuries incurred during rapes. Occasionally, males even try to mate with dead females. Even while they are still paired earlier in the breeding season, males frequently court and attempt to mate with (or rape) females other than their mate. About 3–7 percent of offspring are a result of such nonmonogamous matings, and in some populations multiple parentage occurs in at least 17–25 percent of all broods.