Biological Exuberance: Animal Homosexuality and Natural Diversity

pairs: in one case, two females were seen to mate with each other as often as five times in one day.

Orientation: Because the eggs they lay are usually infertile, it is likely that many female Black-winged Stilts in lesbian pairs are exclusively homosexual, i.e., they do not copulate with males (at least for the duration of their bond). In addition, some females show a persistent orientation toward other females, since they remate with another female if their lesbian partnership breaks up.

Nonreproductive and Alternative Heterosexualities

In addition to long-lasting monogamous pairs, a variety of alternative heterosexual family arrangements occur in Stilts. Black Stilts occasionally form trios of two females and one male (with both females laying eggs), while Black-winged Stilt pairs sometimes adopt chicks from other families and foster-parent them along with their own. Divorce and remating may occur in male-female pairs of Black-winged Stilts, and some males engage in courtship and copulation with females other than their mates. In Black Stilts, heterosexual pairs sometimes separate when their young fledge: the male often takes the juveniles with him as a single parent when he migrates, while the female remains behind. On returning, the male may get back together with his previous partner, or the female may find a new mate. In some intact Black Stilt families, fathers maybe abusive toward their young, behaving aggressively or rejecting their male offspring (although this has so far only been reported in captivity). In both of these Stilt species, individuals often masturbate by mounting an inanimate object (such as a piece of driftwood) and performing copulatory movements. In Black-winged Stilts this behavior may occur with extraordinary frequency— one bird was recorded making 20—30 such masturbatory mounts in one session, roughly once every 30 seconds. Finally, birds sometimes pair with individuals outside of their species: in some populations, about 30 percent of Black Stilts mate with Black-winged Stilts, and hybrids of the two species are common.

Sources

*asterisked references discuss homosexuality/transgender

Cramp, S., and K. E. L. Simmons, eds. (1983) “Black-winged Stilt (Himantopus himantopus).” In Handbook of the Birds of Europe, the Middle East, and North Africa, vol. 3, pp. 36-47. Oxford: Oxford University Press.

Goriup, P. D. (1982) “Behavior of Black-winged Stilts.” British Birds 75:12— 24.

Hamilton, R. B. (1975) Comparative Behavior of the American Avocet and the Black-necked Stilt (Recurvirostridae). Ornithological Monographs no. 17. Washington, DC: American Ornithologists’ Union.

Kitagawa, T. (1989) “Ethosociological Studies of the Black-winged Stilt Himantopus himantopus himantopus. I. Ethogram of the Agonistic Behaviors.” Journal of the Yamashina Institute of Ornithology 21:52—75.

*———(1988a) “Ethosociological Studies of the Black-winged Stilt Himantopus himantopus himantopus. III. Female-Female Pairing.” Japanese Journal of Ornithology 37:63—67.

———(1988b) “Ethosociological Studies of the Black-winged Stilt Himantopus himantopus himantopus. II. Social Structure in an Overwintering Population.” Japanese Journal of Ornithology 37:45—62.

*Pierce, R. J. (1996a) “Recurvirostridae (Stilts and Avocets).” In J. del Hoyo, A. Elliott, and J. Sargatal, eds., Handbook of the Birds of the World, vol. 3: Hoatzin to Auks, pp. 332—47. Barcelona: Lynx Edicions.

———(1996b) “Ecology and Management of the Black Stilt Himantopus novaezelandiae.” Bird Conservation International 6:81—88.

(1986) Black Stilt. Endangered New Zealand Wildlife Series. Dunedin, New Zealand: John McIndoe and New Zealand Wildlife Service.

*Reed, C. E. M. (1993) “Black Stilt.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 2, pp. 769—80. Melbourne: Oxford University Press.

OYSTERCATCHER

IDENTIFICATION: A large (17 inch), stocky shore bird with black upperparts, white underparts, and red-orange bill, eyes, and legs. DISTRIBUTION: Throughout Eurasia; winters in Africa, Middle East, southern Asia. HABITAT: Beaches, salt marshes, rocky coasts, mudflats. STUDY AREAS: The islands of Texel, Vlieland, and Schiermonnikoog, the Netherlands; subspecies H.o. ostralegus.

GOLDEN PLOVER

IDENTIFICATION: A medium-sized (10 inch) sandpiper-like bird with mottled buff and black plumage; adult males have a black face and underparts bordered with white. DISTRIBUTION: Northern Europe; winters south to Mediterranean and North Africa. HABITAT: Tundra, bogs, moors, heath. STUDY AREA: Dorback Moor, Scotland; subspecies P.a. apricaria.

Social Organization

Oystercatchers and Golden Plovers commonly associate in flocks. The mating system typically involves monogamous pair-bonding, although many alternative arrangements also occur (see below). Nonbreeding Oystercatchers tend to aggregate in groups known as CLUBS.

Description

Behavioral Expression: Oystercatchers sometimes participate in same-sex courtship and copulation. This behavior typically occurs within bisexual trios, that is, an association of three birds—two of one sex and one of the other—in which all three members have a bonded sexual relationship. For example, two males and a female sometimes form a trio, and in addition to heterosexual activity between the opposite-sex partners, the two males may court and mount each other. Several different courtship and pair-bonding displays are used in both same-sex and opposite-sex contexts. For example, while walking around each other, two males might perform BALANCING, in which they make seesaw movements with their bodies, or the THICK-SET ATTITUDE, a stylized posture in which the head is drawn down between the shoulders with the tail and back horizontal, all the while bending the legs and making tripping steps. Sometimes two males also perform ritualized nest-building activities as part of their mutual courtship, such as THROWING STRAWS, in which they toss straw and other materials backward, or PRESSING A HOLE, in which they repeatedly sit down, pressing their breasts and wings against the ground as if fashioning a nest. As a prelude to copulation, one male approaches the other in the STEALTHY ATTITUDE, similar to the thick-set attitude except that the head is held to one side and the tail is pressed down and spread. One male may mount and try to copulate with the other, although sometimes his sexual advances are thwarted by an attack from the other male. Interestingly, all three members of such a trio may be nonmonogamous, engaging in heterosexual courtship or copulations with birds other than their primary partners.

Homosexual activities also occur between two female Oystercatchers that form part of a bisexual trio with a male. Most associations of this type start off the way heterosexual trios do, with considerable aggression between the females, but eventually they develop a strong bond with each other. They preen one another while remaining close together and also cooperate (along with their male partner) in mutual defense of their territory. Employing the same behavior patterns seen in heterosexual mating, the two females also regularly copulate with one another: one female approaches the other in a hunched posture, making soft pip-pip noises while her partner tosses her tail upward. Then, while mounting, the female flaps her wings to maintain balance and may push her tail under the other female’s in order to achieve genital (cloacal) contact, at which point she utters soft wee-wee sounds. The two birds may take turns mounting one another, and about 47 percent of lesbian copulations include full genital contact (compared to 67 percent of matings by heterosexual pairs