Biological Exuberance: Animal Homosexuality and Natural Diversity

two females or two females and one male; these make up about 5 percent of all heterosexual bonds. In King Penguins, nonbreeding females may associate with a heterosexual pair and help them raise their chick, who recognizes all three birds as its parents; single parenting is also common. Nonbreeders that aren’t part of trios also occasionally feed chicks belonging to other birds, particularly when the chicks are in CRECHES. These large nursery groups, sometimes containing thousands of chicks, form while the parents are away. Creches also occur in Gentoos, where they are often attended by several adult “guardians.” During the winter, King parents are often gone for long periods on fishing trips, and chicks may not be fed for weeks or months at a time. As many as 10 percent of them perish from this prolonged fasting and starvation. Some parents abandon their chicks or eggs (especially in severe weather), and chicks may also be killed in squabbles between their parents and nonbreeding birds that are trying to “kidnap” them. King Penguins also occasionally “steal” other pairs’ eggs.

Breeding can take its toll on adults as well: male King Penguins fast for more than fifty days during courtship and incubation, losing 10—12 percent of their body weight. In addition, heterosexual copulations are sometimes harassed, with throngs of neighboring birds converging on mating pairs, attacking them and trying to interrupt the sexual activity. Many birds forgo breeding altogether: more than 40 percent of the population each year consists of nonbreeders, and birds generally do not breed every year (primarily because of the unusually long 16—month breeding cycle). Extensive nonbreeding is also a feature of Gentoo populations: up to a quarter of the adults may skip breeding each year, and more than 15 percent of birds breeding late in the season lay infertile clutches. In addition, breeding is delayed for one to two years in younger King and Gentoo Penguins, due to both physiological and social factors. Some Humboldt Penguins remain single and nonbreeding as well, although they may still engage in sexual behavior with other birds.

Other Species

Reciprocal homosexual copulations—involving full genital (cloacal) contact—also occur among male Adelie Penguins (Pygoscelis adeliae) in Antarctica, accompanied by courtship displays such as DEEP BOWING and the ARMS ACT. Following ejaculation by the mounter, the mountee contracts his cloaca, perhaps facilitating movement of his partner’s semen in his genital tract and/or indicating orgasm. Some males who participate in homosexual activity also mate heterosexually.

Sources

*asterisked references discuss homosexuality/transgender

Bagshawe, T. W. (1938) “Notes on the Habits of the Gentoo and Ringed or Antarctic Penguins.” Transactions of the Zoological Society of London 24:185—306.

Bost, C. A., and P. Jouventin (1991) “The Breeding Performance of the Gentoo Penguin Pygoscelis papua at the Northern Edge of Its Range.” Ibis 133:14—25.

*Davis, L. S., F. M. Hunter, R. G. Harcourt, and S. M. Heath (1998) “Reciprocal Homosexual Mounting in Adelie Penguins Pygoscelis adeliae.” Emu 98:136—37.

*Gillespie, T. H. (1932) A Book of King Penguins. London: Herbert Jenkins Ltd.

Kojima, I. (1978) “Breeding Humboldt’s Penguins Spheniscus humboldti at Kyoto Zoo.” International Zoo Yearbook 18:53—59.

*Merritt, K., and N. E. King (1987) “Behavioral Sex Differences and Activity Patterns of Captive Humboldt Penguins.” Zoo Biology 6:129—38.

*Murphy, R. C. (1936) Oceanic Birds of South America, vol. 1, p.340. New York: American Museum of Natural History.

Olsson, O. (1996) “Seasonal Effects of Timing and Reproduction in the King Penguin: A Unique Breeding Cycle.” Journal of Avian Biology 27:7—14.

*Roberts, B. (1934) “The Breeding Behavior of Penguins, with Special Reference to Pygoscelis papua (Forster).” British Graham Land Expedition Science Report 1:195— 254.

Schmidt, C. R. (1978) “Humboldt’s Penguins Spheniscus humboldti at Zurich Zoo.” International Zoo Yearbook 18:47—52.

*Scholten, C. J. (1996) Personal communication.

*———(1992) “Choice of Nest-site and Mate in Humboldt Penguins (Spheniscus humboldti)” SPN (Spheniscus Penguin Newsletter) 5:3—13.

*———(1987) “Breeding Biology of the Humboldt Penguin Spheniscus humboldti at Emmen Zoo.” International Zoo Yearbook 26:198—204.

*Stevenson, M. F. (1983) “Penguins in Captivity.” Avicultural Magazine 89:189— 203 (reprinted in International Zoo News 189 [1985]:17—28).

Stonehouse, B. (1960) “The King Penguin Aptenodytes patagonica of South Georgia. 1. Breeding Behavior and Development.” Falkland Islands Dependencies Survey Scientific Reports 23:1—81.

van Zinderen Bakker, E. M., Jr. (1971) “A Behavior Analysis of the Gentoo Penguin Pygoscelis papua.” In E. M. van Zinderen Bakker Sr., J. M. Winterbottom, and R. A. Dyer, eds., Marion and Prince Edward Islands: Report on the South African Biological and Geological Expedition, pp. 251—72. Cape Town: A. A. Balkema.

Weimerskirch, H., J. C. Stahl, and P. Jouventin (1992) “The Breeding Biology and Population Dynamics of King Penguins Aptenodytes patagonica on the Crozet Islands.” Ibis 134:107—17.

*Wheater, R. J. (1976) “The Breeding of Gentoo Penguins Pygoscelis papua in Edinburgh Zoo.” International Zoo Yearbook 16:89—91.

Williams, T. D. (1996) “Mate Fidelity in Penguins.” In J. M. Black, ed., Partnerships in Birds: The Study of Monogamy, pp. 268—85. Oxford: Oxford University Press.

———(1995) The Penguins: Spheniscidae. Oxford: Oxford University Press.

Williams, T. D., and S. Rodwell (1992) “Annual Variation in Return Rate, Mate and Nest-Site Fidelity in Breeding Gentoo and Macaroni Penguins.” Condor 94:636—45.

Wilson, R. P., and M.-P. T. Wilson (1990) “Foraging Ecology of Breeding Spheniscus Penguins.” In L. S. Davis and J. T. Darby, eds., Penguin Biology, pp. 181-206. San Diego: Academic Press.

BIRDS OF PREY AND GAME BIRDS

KESTREL

IDENTIFICATION: A small falcon (12-15 inches) having chestnut plumage spotted with black, and a gray head and tail in males. DISTRIBUTION: Throughout Eurasia and Africa. HABITAT: Variable, including plains, steppe, woodland, wetlands. STUDY AREA: Niva, Denmark; subspecies F.t. tinnunculus.

GRIFFON VULTURE

IDENTIFICATION: A large vulture (wingspan up to 9 feet) with a white head and neck and brown plumage. DISTRIBUTION: Southern Europe, North Africa, Middle East to Himalayas. HABITAT: Mountains, steppe, forest. STUDY AREAS: Berlin Zoo; Jonte Gorge and other regions of the Massif Central Mountains, France; Lumbier, Spain; subspecies G.f. fulvus.

Social Organization

During early spring through summer, Kestrels associate as mated pairs that each have their own territory; there is also a significant subpopulation of nonbreeding birds. Outside of the mating season, males and females are