Biological Exuberance: Animal Homosexuality and Natural Diversity

Communally Nesting Acorn Woodpecker.” Science 206:1103–5.

*MacRoberts, M. H., and B. R. MacRoberts (1976) Social Organization and Behavior of the Acorn Woodpecker in Central Coastal California. Ornithological Monographs no. 21. Washington, D.C.: American Ornithologists’ Union.

Mumme, R. L., W. D. Koenig, and F. A. Pitelka (1988) “Costs and Benefits of Joint Nesting in the Acorn Woodpecker.” American Naturalist 131:654–77.

———(1983) “Reproductive Competition in the Communal Acorn Woodpecker: Sisters Destroy Each Other’s Eggs.” Nature 306:583–84.

Mumme, R. L., W. D. Koenig, R. M. Zink, and J.A. Marten (1985) “Genetic Variation and Parentage in a California Population of Acorn Woodpeckers.” Auk 102:305–12.

*Neelakantan, K. K. (1962) “Drumming by, and an Instance of Homo-sexual Behavior in, the Lesser Gold- enbacked Woodpecker (Dinopium benghalense).” Journal of the Bombay Natural History Society 59:288–90.

Short, L.L. (1982) Woodpeckers of the World. Delaware Museum of Natural History Monograph Series no. 4. Greenville, Del.: Delaware Museum of Natural History.

———(1973) “Habits of Some Asian Woodpeckers (Aves, Pisidae).” Bulletin of the American Museum of Natural History 152:253–364.

Stacey, P. B. (1979) “Kinship, Promiscuity, and Communal Breeding in the Acorn Woodpecker.” Behavioral Ecology and Sociobiology 6:53–66.

Stacey, P. B., and T. C. Edwards, Jr. (1983) “Possible Cases of Infanticide by Immigrant Females in a Group- breeding Bird.” Auk 100:731–33.

Stacey, P. B., and W. D. Koenig (1984) “Cooperative Breeding in the Acorn Woodpecker.” Scientific American 251:114–21.

Stanback, M. T. (1994) “Dominance Within Broods of the Cooperatively Breeding Acorn Woodpecker.” Animal Behavior 47:1121–26.

*Troetschler, R. G. (1976) “Acorn Woodpecker Breeding Strategy as Affected by Starling Nest-Hole Competition.” Condor 78:151–65.

Winkler, H., D. A. Christie, and D. Nurney (1995) “Black-rumped Flameback (Dinopium benghalense).” In Woodpeckers: A Guide to the Woodpeckers of the World, pp. 375–77. Boston: Houghton Mifflin.

PIED KINGFISHER

IDENTIFICATION: A robin-sized, crested bird with speckled black-and-white plumage and a long bill. DISTRIBUTION: Sub-Saharan Africa, the Middle East, India, Southeast Asia. HABITAT: Lakes and rivers. STUDY AREA: Basse Casamance region of Senegal; subspecies C.r. rudis.

BLUE-BELLIED ROLLER

IDENTIFICATION: A stocky, 14-inch bird with dark blue plumage, a long, turquoise, forked tail, and a creamy white head and breast DISTRIBUTION: West Africa. HABITAT: Savanna woodland. STUDY AREA: Basse Casamance region of Senegal.

Social Organization

Pied Kingfishers sometimes gather in flocks of 80 or more birds, and outside of the mating season they associate in small groups. Breeding birds form monogamous pairs, but there is a large population of nonbreeding males as well, many of whom help heterosexual pairs raise their young. Blue-bellied Rollers live in pairs or small groups of 3-13 birds, which are probably extended families or clans; mating may occur promiscuously among several group members.

Description

Behavioral Expression: In Pied Kingfishers, two males sometimes develop a pair-bond and may engage in homosexual mounting and copulation attempts. Homosexual mounting can also occur among males that are not bonded to each other. In all cases, homosexual activity is found among nonbreeding males, of which there are several distinct categories. Some males are HELPERS, who assist heterosexual pairs in raising their young. There are two types of such helpers: PRIMARY helpers, adult birds who help their parents; and SECONDARY helpers, who are unrelated to the pairs they help. In addition, some nonbreeding birds are nonhelpers, who do not assist heterosexual pairs at all. Homosexual pairing probably occurs mostly in the latter group, since primary helpers are devoted to assisting their parents and are also often hostile toward secondary helpers, openly attacking and fighting with them. Some homosexual behavior may also take place among secondary helpers, although this is less likely, since such males are usually preoccupied with feeding females in the pairs they assist (though their parenting duties are usually less extensive than those of primary helpers).

A remarkable form of ritualized sexual behavior occurs among Blue-bellied Rollers, and in some cases the participating birds are of the same sex. One bird mounts the other as in regular copulation, beating its wings and sometimes grabbing in its bill the neck or head feathers of its partner. The mounter lowers its tail while the mountee droops its wings and raises its tail, in some cases achieving cloacal (genital) contact. In almost three- quarters of the cases, mounting is reciprocal (the mountee becoming the mounter and vice versa); reciprocal mounting may be more common between birds of the opposite sex, however. Sometimes, mounting with exchange of positions is performed repeatedly, with as many as 28 mounts alternating between the partners in succession. This mounting behavior is often a ritualized display performed for other birds, and sometimes the tail movements and other gestures characteristic of full sexual behavior are more stylized or attenuated. Mounting may be accompanied by a number of dramatic aerial displays (often considered signs of aggression), including acrobatic chases, SOARS (rapid ascents with wings angled in a V-shape, just prior to being “caught” by a pursuing bird), and swoops (breathtaking plummets with folded wings). Birds may also utter loud, mechanical-sounding RATTLES as well as screaming RASP notes during mounting or the associated aerial displays.

Frequency: Homosexual bonding and mounting probably occur only occasionally among Pied Kingfishers. Ritual mounting behavior is common among Blue-bellied Rollers, occurring throughout the year; the exact proportion of mounting that is same-sex, however, is not known.

Orientation: In some populations of Pied Kingfishers, about 30 percent of the birds are neither breeders nor helpers, while about 18 percent are secondary helpers—these are the segments in which male homosexual activity is found, although probably only a fraction of these birds are involved. Although secondary helpers often go on to mate heterosexually, it is not known whether the same is true of nonhelpers or birds that participate in homosexual activity. However, because of the relatively short life span (one to three years) and high mortality rate of this species, it is likely that at least some males are involved in homosexual activity for most of their lives without ever mating heterosexually.

Nonreproductive and Alternative Heterosexualities

As discussed above, there is a large segment of nonbreeders in the Pied Kingfisher population: as many as 45-60 percent of males do not mate heterosexually. Remarkably, studies have shown that the reproductive systems of primary helpers are actually physiologically suppressed, since they have reduced male hormone levels, small testes, and no sperm production. Only one in three primary helpers goes on to mate after being a helper, and it is likely that some never breed for their entire lives. In contrast, secondary helpers do not have dormant reproductive systems, but are in most cases simply unable to find female mates due to the greater proportion of males in most populations. Because secondary helpers are not genetically related to the birds they assist, a large number of Pied Kingfishers are involved in “foster-parenting.”

Sexual activity between male and female Blue-bellied Rollers is notable for its nonreproductive components: it occurs at all times of the year (not just during the breeding season), and it often involves nonprocreative REVERSE mounts or mounting without genital contact. In addition, multiple copulations—far in excess of what is