Biological Exuberance: Animal Homosexuality and Natural Diversity

*———(1959) “Die Balz der Schmuckvogel (Pipridae) [The Mating Ritual of Jewel Birds].” Journal fur Ornithologie 100:269–302.

*Snow, D. W. (1976) The Web of Adaptation: Bird Studies in the American Tropics. New York: Quadrangle /New York Times Book Co.

———(1971) “Social Organization of the Blue-backed Manakin.” Wilson Bulletin 83:3–38.

*———(1963) “The Display of the Blue-backed Manakin, Chiroxiphia pareola, in Tobago, W.I.” Zoologica 48:167–76.

IDENTIFICATION: Small (5–7 inch) birds with brown and rufous plumage and a bluish gray patch around the eyes; Ocellateds have a distinctive scalloped pattern on the back feathers. DISTRIBUTION: Central America and northwestern South America from Honduras to Ecuador. HABITAT: Rain forest undergrowth. STUDY AREA: Barro Colorado Island, Panama.

Social Organization

Antbirds get their name because they follow large swarms of army ants for food, often in flocks containing several different bird species. Both Bicolored and Ocellated Antbirds form monogamous pairs that are generally long-lasting. In addition, Ocellated Antbirds live in a complex extended family or “clan” structure, typically containing up to three generations of males and their mates. Females emigrate from these units to join other clans, while males often return to their extended family once they have found mates.

Description

Behavioral Expression: Male homosexual pairs are a distinctive feature of Bicolored and Ocellated Antbird social life. Usually the pair-bond is initiated and strengthened (as in heterosexual pairs) when one male COURTSHIP-FEEDS the other, that is, ritually presents him with a “gift” of food (usually an insect or spider). In Ocellated Antbirds, males who court each other this way often adopt a characteristic pose (also used in heterosexual courtship)—ruffled throat feathers, stiff neck and upright posture, fluffed-out body feathers, with tail and legs spread. They also CAROL, producing a series of up to 15 whistled notes that decrease in pitch (sounding like chee chee chew chew). Unlike heterosexual mates, male partners typically reciprocate courtship feeding by passing the food gift back and forth between them. Homosexual courtship-feeding in Bicolored Antbirds is distinct from the heterosexual pattern in a number of other ways as well: either partner may initiate the activity in a male pair, and courtship-feeding is usually accompanied by CHIRPING—brief, musical cheup notes. In heterosexual pairs, only the male feeds the female, and the partners typically utter GROWLS during courtship-feeding (a rapid hissing or grunting noise composed of rough chauhh notes). Once paired, two males are constant companions, visiting ant swarms together and foraging side by side much as opposite-sex mated pairs do. Homosexual pair- bonds are sometimes long-lasting associations, persisting for many years. Partners may both be adults, or an older bird may pair with a younger one. In Ocellated Antbirds, father-son courtship-feedings also sometimes occur when a younger male remains within the clan structure.

Frequency: In Bicolored Antbirds, an estimated 2-3 percent of all pairs in some populations are composed of two males, and homosexual pairs may constitute up to 4-6 percent of the total number of pairs in any given year. The incidence of male pairs in Ocellated Antbirds is probably comparable.

Orientation: Approximately 5-14 percent of male Bicolored Antbirds may participate in a homosexual pairing or courtship at some point in their life. In both species, some males exhibit sequential bisexuality. In a few cases, for example, males have been mated to a female prior to their homosexual pairing (they may even have fathered young, and some are widowers), or they may go on to mate with a female when a homosexual pairing breaks up. Other males, however, show no signs of participating in heterosexual mating, and these birds may be involved exclusively in homosexual pairs, at least for a portion of their lives.

Nonreproductive and Alternative Heterosexualities

In both Bicolored and Ocellated Antbirds, significant numbers of birds are nonbreeding. As many as 45 percent of adult Bicolored males may not be heterosexually paired in any given year, and some males fail to acquire a mate for six or more years in a row. Younger males may delay their reproductive careers for up to a year after reaching sexual maturity—by remaining “at home” in their clans (Ocellateds) or wandering solitarily (Bicoloreds). In addition, male Antbirds have been known to live to a relatively old age—more than 11 years in Bicoloreds and Ocel- lateds. For a few individuals who have lost their female partners (either through death or divorce), this may be a postreproductive period in their lives. In addition to females leaving their mates for younger males, divorce and mate-switching also occasionally happen in adult Bicolored and newly paired Ocellated Antbirds. Often, a divorce is initiated by “extramarital” courtship between a mated female and an unpaired male. The extended families of Ocellated Antbirds also sometimes break up: heterosexual pairs wander off from the clan if they have not been able to breed successfully, or grandparents isolate themselves from their relatives. Heterosexual relations within a pair are not always smooth either: in Bicoloreds, for example, males are often distinctly hostile to their female mates. This is especially true early in their pair-bond, when he may aggressively “blast” her off her perch with hissing and snapping. Female Ocellated Antbirds have also been observed steadfastly refusing the courtship and copulatory advances of males. Finally, a number of incestuous activities have been documented in these species, including courtship and attempted copulation between Ocellated males and their mothers, and courtship of Bicolored daughters by their fathers.

A male Ocellated Antbird (left) “courtship-feeding” his male pair-mate

Sources

*asterisked references discuss homosexuality/transgender

Willis, E.O. (1983) “Longevities of Some Panamanian Forest Birds, with Note of Low Survivorship in Old Spotted Antbirds (Hylophylax naevioides).” Journal of Field Ornithology54:413-14.

*———(1973) The Behavior of Ocellated Antbirds. Smithsonian Contributions to Zoology no. 144. Washington, D.C.: Smithsonian Institution Press.

*———(1972) The Behavior of Spotted Antbirds. Ornithological Monographs 10. Washington, D.C.: American Ornithologists’ Union.

*———(1967) The Behavior of Bicolored Antbirds. University of California Publications in Zoology 79. Berkeley: University of California Press.

IDENTIFICATION: A small (5 inch), plain olive-green bird with a long tail and an ocher- or tawny- colored lower breast. DISTRIBUTION: From Mexico south to the Amazon in South America; Trinidad and Tobago. HABITAT: Humid lowland forests, open shrubbery. STUDY AREA: Corcovado National Park, Costa Rica; subspecies M.o. dyscola.

Social Organization

Ocher-bellied Flycatchers have a complex social organization, with three distinct categories of males. About 42 percent of males are TERRITORIAL, defending “courts” in the foliage within which they perform courtship displays; sometimes groups of two to six territorial males display close to each other in a LEK formation. Another 10