———(1993) “A Case of Polyandry in the Blue Tit: Female Extra-Pair Behavior Results in Extra Male Help.” Ornis Scandinavica 24:246—49.
Kempenaers, B., G. R. Verheyen, and A. A. Dhondt (1997) “Extrapair Paternity in the Blue Tit (Parus caeruleus): Female Choice, Male Characteristics, and Offspring Quality.” Behavioral Ecology 8:481-92.
———(1995) “Mate Guarding and Copulation Behavior in Monogamous and Polygynous Blue Tits: Do Males Follow a Best-of-a-Bad-Job Strategy?” Behavioral Ecology and Sociobiology 36:33—42.
Krieg, D. C. (1971) The Behavioral Patterns of the Eastern Bluebird (Sialia sialis). New York State Museum and Science Service Bulletin no. 415. Albany: University of the State of New York.
Massa, R., L. Bottoni, L. Fornasari, and N. Sacchi (1995) “Studies on the Socio-Sexual and Territorial System of the Red-backed Shrike.” Proceedings of the Western Foundation of Vertebrate Zoology 6:172-75.
Meek, S. B., R. J. Robertson, and P. T. Boag (1994) “Extrapair Paternity and Intraspecific Brood Parasitism in Eastern Bluebirds Revealed by DNA Fingerprinting.” Auk 111:739—44.
*Owen, J. H. (1946) “The Eggs of the Red-backed Shrike.” Oologists’ Record 20:38-43.
*Pinkowski, B.C. (1977) “‘Courtship Feeding’ Attempt Between Two Male Eastern Bluebirds.” Jack-Pine Warbler 55:45—46.
*Pounds, H. E. (1972) “Two Red-backed Shrikes Laying in One Nest.” British Birds 65:357—58.
*Sætre, G.-P., and T. Slagsvold (1993) “Evidence for Sex Recognition from Plumage Color by the Pied Flycatcher, Ficedula hypoleuca.” Animal Behavior 44:293—99.
*Slagsvold, T., and G.-P. Sætre (1991) “Evolution of Plumage Color in Male Pied Flycatchers (Ficedula hypoleuca): Evidence for Female Mimicry.” Evolution 45:910—17.
Stanback, M. T., and W. D. Koenig (1992) “Cannibalism in Birds.” In M.A. Elgar and B. J. Crespi, eds., Cannibalism: Ecology and Evolution Among Diverse Taxa, pp. 277-98. Oxford: Oxford University Press.
*Zeleny, L. (1976) The Bluebird: How You Can Help Its Fight for Survival. Bloomington: Indiana University Press.
SPARROWS, BLACKBIRDS, AND CROWS
GRAY-CAPPED SOCIAL WEAVER
IDENTIFICATION: A grayish buff, sparrow-sized bird with a pale gray-white crown. DISTRIBUTION: Northeast Africa. HABITAT: Bush, acacia savanna. STUDY AREA: Olorgesailie National Prehistoric Site, Kenya; subspecies P.a. arnaudi.
SOCIABLE WEAVER
IDENTIFICATION: A drab, sparrowlike bird with brownish gray plumage and a black throat patch. DISTRIBUTION: Southwestern Africa. HABITAT: Scrub, savanna. STUDY AREA: University of California—Los Angeles.
BISHOP BIRDS
IDENTIFICATION: Small, sparrowlike birds with black and brown plumage and various scarlet, red, or reddish orange patches on the chest, nape, crown, and rump. DISTRIBUTION: Sub-Saharan Africa. HABITAT: Moist grassland. STUDY AREAS: Several locations in South Africa, including near Cape Town, Howick, and Bloemfontein; University of Cape Town and University of Bielefeld.
Social Organization
Weaverbirds are named for the intricate—and often colossal—nests they weave. Sociable Weavers build giant condominium-like structures containing many nest chambers; each chamber may house up to 5 birds, while the entire colony can contain as many as 500 birds. Colonies of Gray-capped Social Weavers consist of family groups that each build several hanging nests (one is used as an actual nesting chamber, the others for sleeping). Several groups occupy the same tree, each situated in its own cluster. In both Gray-caps and Sociable Weavers, breeding birds form pair-bonds, and “helper” birds may assist them in their parenting duties. Adult male Bishop Birds establish territories during the breeding season on which they weave elaborate nests and court potential mates. The breeding system of Bishop Birds is polygynous: males mate with numerous females, each of whom lays eggs in one of the nests on his territory, but the male himself does not participate in any parental duties. Outside of the breeding season, Bishop Birds typically socialize in large, often mixed-species flocks.
Description
Behavioral Expression: Male Gray-capped Social Weavers and Sociable Weavers sometimes participate in homosexual copulations. In Gray-caps, birds who participate in same-sex mounting are usually heterosexually paired males, often high-ranking individuals living in the same colony (tree). One male may fly from his home group in the tree to another male’s residence, inviting him to mate by holding his body horizontal, raising his head and tail upward, and drooping and vibrating his wings. The other male then mounts him and proceeds to engage in a complete copulation sequence, probably including cloacal (genital) contact. Mounting between males occurs in Sociable Weavers as well, and about 9 percent of such mounts are also full copulations in which the mounted male crouches, quivers his wings, and moves his tail to the side as the mounting male lowers his tail (probably to achieve genital contact). Usually higher-ranking males mount lower-ranking ones, but all males both mount and are mounted by other males (to varying degrees). In addition, some males appear to form “companionships” with each other. Although males do not generally permit other males to roost with them in their nesting chambers, occasionally two males regularly associate with one another and sleep together in the same nest. This can occur even if one of the males is already paired to a female, in which case all three birds occupy the nest together. The two males may remain together for years, even cooperating in attacking other birds together. Some male “companions” participate in mountings and copulations with each other, but in other cases males do not seem to preferentially engage in sexual behavior with their companion.
On their nesting territories, male Red Bishop Birds court both females and males, the latter usually being younger males who have brown plumage (as do females). Courtship consists of two components: a flying display and a perched display. When a young male appears near his territory, an adult male approaches in a distinctive BUMBLE-FLIGHT, in which he fluffs up all of his plumage and flies with slow wingbeats, resembling a bumble-bee. The bird’s bright red back or epaulet feathers are prominently displayed, and the bumble-flying may be accompanied by singing or a distinctive noise made by his flapping wings. Sometimes males bumble-fly toward another adult male rather than a younger male. After the display flight, the adult male lands near the other male and begins the SWIVEL DISPLAYS: he hops and twists around his perch, approaching the object of his attentions with ruffled plumage and a rattling call—a continuous stream of notes that sounds like zik-zik-zik. No homosexual copulations have been observed in this species in the wild, but heterosexual matings are not commonly seen either. In captivity Orange Bishop Birds—both adults and younger males—sometimes do try to mount younger males (including males of the closely related Golden Bishop Bird, Euplectes afer). In a homosexual encounter, one male approaches the other while pumping his body up and down and ruffling his feathers, followed by an attempt to copulate with the other male (who usually rejects his advances).
A male Red Bishop Bird displaying fluffed “bumblebee” plumage, used during courtships with same- and opposite-sex partners
Frequency: In Sociable Weavers studied in captivity, as much as three-quarters of all mounting activity is between males, and three out of five full copulations are homosexual. The occurrence of same-sex mounting in wild birds of this species is not known, but its prevalence is probably comparable (especially since heterosexual activity is also apparently infrequent). In one study of wild Gray-capped Social Weavers, all sexual activity that was observed took place between males. In Red Bishops, approximately 6 percent of courtship bumble-flights are directed by one adult male toward another adult male; courtship of younger males probably occurs more often than this.
Orientation: Male Gray-capped Social Weavers that copulate with other males also mate and pair with females (and in fact may engage in homosexual activity while they are heterosexually paired). The same is true for some Sociable Weavers, although most males in this species mount both males and females, even if they are not paired. However, relatively few males participate in full heterosexual copulations, and those that do appear to have higher rates of homosexual activity as well. To the extent that they court or attempt to mount both males and females, some male Bishops are also bisexual. However, the males they pursue are usually indifferent, at best, to their approaches, indicating perhaps a more heterosexual orientation on their part.
Nonreproductive and Alternative Heterosexualities
In Gray-capped Social Weavers (and occasionally in Sociable Weavers), nonbreeding birds often help heterosexual pairs build their nest and feed their young. Some of these “helpers” are the pairs’ young from a previous season who are delaying their own reproductive careers, while others are fully adult birds (who help out in about 18 percent of all feedings). Some nonbreeding youngsters, however, do not help their parents. Sociable Weavers may participate in nonmonogamous heterosexual mountings (in addition to the homosexual matings described above). Although most birds are probably faithful to their partners, some males in captivity have been observed mounting and copulating with females other than their mates. Female Red Bishops occasionally refuse to allow a male to mount them, vigorously pecking and displaying threat postures to repel him. In addition, males often court Bishops of other species, who are not usually attracted by such interspecies displays. Finally, female Red Bishops have been observed cannibalizing both their own and others’ nests, eating some or all of the eggs.
Other Species
Adult male Red-shouldered Widowbirds (Euplectes axillaris) also sometimes court younger males.
Sources
*asterisked references discuss homosexuality/transgender
*Collias, E. C, and N. E. Collias (1980) “Individual and Sex Differences in Behavior of the Sociable Weaver Philetairus socius.” In D. N. Johnson, ed., Proceedings of the Fourth Pan-African Ornithological Congress (Seychelles, 1976), pp. 243—51. Johannesburg: Southern African Ornithological Society.
*———(1978) “Nest Building and Nesting Behavior of the Sociable Weaver Philetairus socius.” Ibis 120:1—15.
*Collias, N. E., and E. C. Collias (1980) “Behavior of the Gray-capped Social Weaver (Psuedonigrita arnaudi) in Kenya.” Auk 97:213—26.
Craig, A. J. F. K. (1982) “Mate Attraction and Breeding Success in the Red Bishop.” Ostrich 53:246-48.
*———(1980) “Behavior and Evolution in the Genus Euplectes.” Journal für Ornithologie 121:144—61.
*———(1974) “Reproductive Behavior of the Male Red Bishop Bird.” Ostrich 45:149—60.
Craig, A. J. F. K., and A. J. Manson (1981) “Sexing Euplectes Species by Wing-Length.” Ostrich 52:9—16.
Maclean, G. L. (1973) “The Sociable Weaver.” Ostrich 44:176—261.
Roberts, C. (1988) “Little Bishop Birds (Euplectes orix) in a Lafia Garden—Tom, Dick, Harry, and Fred.” Nigerian Field 53:11—22.
Skead, C. J. (1959) “A Study of the Redshouldered Widowbird Coliuspasser axillaris axillaris (Smith).” Ostrich 30:13—21.
———(1956) “A Study of the Red Bishop.” Ostrich 27:112—26.
Woodall, P. F. (1971) “Notes on a Rhodesian Colony of the Red Bishop.” Ostrich 42:205—10.
HOUSE SPARROW, BROWN-HEADED COWBIRD
IDENTIFICATION: The familiar black-bibbed sparrow; Cowbird is iridescent black with a dark brown head. DISTRIBUTION: Throughout most of North and South America, Eurasia (House Sparrow); North and Central America (Cowbird). HABITAT: Woodland, prairie, farmland, human habitation. STUDY AREAS: Near Stillwater, Oklahoma, and Long Island, New York; subspecies M.a. ater and M.a. artemisiae.
WATTLED STARLING
IDENTIFICATION: Light gray plumage, black wings and tail, and (in some birds) bare yellow head and fleshy black wattles. DISTRIBUTION: Eastern and southern Africa. HABITAT: Savanna, grassland, woodland. STUDY AREAS: University of Mainz and in Nieder-Olm, Germany.
Social Organization
Wattled Starlings usually associate in small, nomadic flocks, although up to a thousand birds may gather together to pursue locust swarms. Similarly, breeding colonies may contain thousands of nests when locusts are available, but usually birds nest in smaller groups containing a maximum of 400 pairs. Most individuals form monogamous pair-bonds, as do House Sparrows (who also generally nest in colonies). Brown-headed Cowbirds have a highly variable mating system: in many populations birds form (usually monogamous) pair-bonds, while in others they are promiscuous or form polygamous bonds with several individuals.
Description
Behavioral Expression: Male Brown-headed Cowbirds sometimes solicit homosexual copulations from male House Sparrows. Cowbirds commonly invite birds of other species to preen them, but occasionally an interspecies encounter includes homosexual mounting when a House Sparrow is involved. This extraordinary behavior typically begins with a male Cowbird adopting a characteristic HEAD-DOWN posture next to a Sparrow, in which he bows his head, touching his lower bill to his breast feathers while crouching slightly and raising his wings a bit at the shoulders. The House Sparrow then mounts the Cowbird, grasping his head feathers in his beak while attempting to copulate. If he shows signs of leaving or lack of interest after a single mounting, the Cowbird will immediately resume the invitation posture next to him, insistently nudging the Sparrow with his head and persistently following him until he mounts again. This may continue for an extended time, with repeated homosexual mountings (five or more) occurring in a single session.
Homosexual courtships occasionally occur in Wattled Starlings. Males sometimes select another male as the object of their attentions, displaying to him with a number of stylized postures. Among these are the LATERAL DISPLAY, in which the male turns sideways and lets his wings hang down at his side (exposing their white feathers); the FRONTAL DISPLAY, where the courting male fluffs up his belly and back feathers, raising and quivering his wings while spreading his tail; and the distinctive VULTURE POSTURE, in which he stretches his entire body vertically while puffing out his breast feathers and tightly folding his wings against his sides like a vulture. A form of plumage transvestism also occurs in this species, in which some females develop a male appearance. Most males have a special seasonal nuptial plumage, growing two pendulous wattles from either side of their beaks and losing most of the feathers from their head, thereby exposing the yellow or black skin and two fleshy, comblike growths on the forehead. This feather loss has even been described as a form of “male pattern baldness” akin to the type of hair loss found in humans, and indeed it is regulated by male hormones (as is human baldness). While the majority of females never exhibit these plumage characteristics, a few females do acquire a male appearance with feather loss, wattles, and combs.
Frequency: Brown-headed Cowbirds regularly perform the head-down display toward other species in the wild, and approximately 36 percent of such displays are directed by male Cowbirds toward male House Sparrows; however, Sparrows respond with homosexual mounting probably only sporadically. Similarly, homosexual courtship is in all likelihood only an occasional occurrence in Wattled Starlings. About 2—10 percent of female Wattled Starlings are transgendered, exhibiting fairly complete wattles and/or baldness. Other females appear to fall along a continuum of plumage characteristics, with some individuals showing only partial wattle development or incomplete baldness.
A male Brown-headed Cowbird in the “head-down” posture (right) inviting a male House Sparrow to mount him
Orientation: In all three of these species, not enough is yet known about the life histories of individuals participating in homosexual activity to determine their overall sexual orientation profiles. However, at least some male Wattled Starlings appear to preferentially select other males to court.
Nonreproductive and Alternative Heterosexualities
Although most heterosexual Wattled Starlings form monogamous pairs, occasionally males court and mate with females other than their mate. This may result in a female raising her young as a single parent if she is not paired to the male she mates with. The male sexual cycle is especially pronounced in this species, signaled by the seasonal development of wattles and baldness. House Sparrows often engage in multiple copulations during the same mating bout: a male may mount a female and achieve genital contact up to 30 times in rapid succession. In addition, promiscuous matings are quite common in this species: more than a quarter of all nests contain at least one chick sired by a bird other than its mother’s mate. Some of these are the result of forced matings that occur during COMMUNAL DISPLAYS, in which “gangs” of up to ten males chase a female, peck at her genitals, and try to mount her. Such displays and the associated sexual activity often take place during nonfertilizable periods as well. Courting male Cowbirds also frequently harass females, and on average only about 12 percent of heterosexual consortships in this species culminate in copulation. In pair-bonding populations of Brown-headed Cowbirds, about 16 percent of courtships are actually between birds not paired to one another, and some promiscuous matings occur as well. In both this species and House Sparrows, a few pairs switch mates during the breeding season, and a subset of birds (about 5—6 percent) are polygamous.
Large numbers of male Cowbirds are nonbreeders: more than half of all males in some populations are unpaired, and only a third of males actually copulate with females in some years. Brown-headed Cowbirds are also BROOD PARASITES, which means that females always lay their eggs in the nests of other bird species and take no part in raising their own young. Infanticide occurs in 9—12 percent of House Sparrow nests, often when a female who has lost her mate pairs with a new male (who pecks her young to death in order to father his own offspring). Females in polygamous trios also occasionally kill one another’s nestlings. Sometimes, however, a female whose mate has been replaced by an infanticidal male will stop laying eggs (by interrupting or delaying ovulation) in order not to lose any more young, and some replacement males adopt rather than kill their mate’s young.
Other Species
Male Sharp-tailed Sparrows (Ammodramus caudacutus), a North American species, sometimes mount other males. Adolescent male Yellow-rumped Caciques (Cacicus cela), a South American blackbird, frequently mount fledglings of both sexes. Sexual behavior toward these younger birds is usually part of an overall pattern of harassment, in which the adolescent males (often in groups) chase, peck, attack, and sometimes even knock fledglings from their perches (often resulting in their death by drowning if they fall into water). About 36 percent of such harassments (and the associated sexual behavior) involve same-sex interactions.
Sources
*asterisked references discuss homosexuality/transgender
Craig, A. J. F. K. (1996) “The Annual Cycle of Wing Moult and Breeding in the Wattled Starling Creatophora cinerea.” Ibis 138:448—54.
Darley, J. A. (1978) “Pairing in Captive Brown-headed Cowbirds (Molothrus ater).” Canadian Journal of Zoology 56:2249—52.
*Dean, W. R. J. (1978) “Plumage, Reproductive Condition, and Moult in Non-Breeding Wattled Starlings.” Ostrich 49:97-101.
Friedmann, H. (1929) The Cowbirds: A Study in the Biology of Social Parasitism. Springfield, Ill.: Charles C. Thomas.
*Greenlaw, J. S., and J. D. Rising (1994) “Sharp-tailed Sparrow (Ammodramus caudacutus).” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21 st Century, no. 112. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.
*Griffin, D. N. (1959) “Apparent Homosexual Behavior Between Brown-headed Cowbird and House Sparrow.” Auk 76:238—39.
*Hamilton, J. B. (1959) “A Male Pattern Baldness in Wattled Starlings Resembling the Condition in Man.” Annals of the New York Academy of Sciences 83:429-47.
Laskey, A. R. (1950) “Cowbird Behavior.” Wilson Bulletin 62:157-74.
Liversidge, R. (1961) “The Wattled Starling (Creatophora cinerea [Menschen]).” Annals of the Cape Provincial Museums 1:71—80.
Lowther, P. E. (1993) “Brown-headed Cowbird (Molothrus ater).” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21st Century, no. 47. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.
Lowther, P. E., and C. L. Cink (1992) “House Sparrow (Passer domesticus).” In A. Poole, P. Stettenheim, and F. Gill, eds., The Birds of North America: Life Histories for the 21 st Century, no. 12. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.
Møller, A. P. (1987) “House Sparrow, Passer domesticus, Communal Displays.” Animal Behavior 35:203—10.
*Robinson, S. K. (1988) “Anti-Social and Social Behavior of Adolescent Yellow-rumped Caciques (Icteri-nae: Cacicus cela).” Animal Behavior 36:1482-95.
Rothstein, S. I. (1980) “The Preening Invitation or Head-Down Display of Parasitic Cowbirds: II. Experimental Analysis and Evidence for Behavioral Mimicry.” Behavior 75:148—84.
Rothstein, S. I., D.A. Yokel, and R. C. Fleischer (1986) “Social Dominance, Mating and Spacing Systems, Female Fecundity, and Vocal Dialects in Captive and Free-Ranging Brown-headed Cowbirds.” Current Ornithology 3:127—85.
Scott, T. W, and J. M. Grumstrup-Scott (1983) “Why Do Brown-headed Cowbirds Perform the Head-Down Display?” Auk 100:139—48.
*Selander, R. K., and C. J. La Rue, Jr. (1961) “Interspecific Preening Invitation Display of Parasitic Cowbirds.” Auk 78:473—504.
*Sontag, W.A., Jr. (1991) “Habitusunterschiede, Balzverhalten, Paarbildung, und Paarbindung beim Lap-penstar Creatophora cinerea [Behavior Differences, Courtship, Pair Formation, and Pair Bonding in the Wattled Starling].” Acta Biologica Benrodis 3:99—114.
———(1978/79) “Remarks Concerning the Social Behavior of Wattled Starlings, Creatophora cinerea (Menschen).” Journal of the Nepal Research Center 2/3:263—68.
Teather, K. L., and R. J. Robertson (1986) “Pair Bonds and Factors Influencing the Diversity of Mating Systems in Brown-headed Cowbirds.” Condor 88:63—69.
Uys, C. J. (1977) “Notes on Wattled Starlings in the Western Cape.” Bokmakierie 28:87—89.
Veiga, J. P. (1993) “Prospective Infanticide and Ovulation Retardation in Free-Living House Sparrows.” Animal Behavior 45:43—46.
———(1990) “Infanticide by Male and Female House Sparrows.” Animal Behavior 39:496-502.
Wetton, J. H., and D.T. Parkin (1991) “An Association Between Fertility and Cuckoldry in the House Sparrow, Passer domesticus.” Proceedings of the Royal Society of London, Series B 245:227-33.
Yokel, D. A. (1986) “Monogamy and Brood Parasitism: An Unlikely Pair.” Animal Behavior 34:1348—58.
Yokel, D. A., and S. I. Rothstein (1991) “The Basis for Female Choice in an Avian Brood Parasite.” Behavioral Ecology and Sociobiology 29:39—45.
BLACK-BILLED MAGPIE
IDENTIFICATION: A pigeon-sized, crowlike bird with striking iridescent, black-and-white plumage and a long, greenish purple tail. DISTRIBUTION: Eurasia, North Africa, western North America. HABITAT: Woodland, scrub, grassland, savanna. STUDY AREAS: Haren, the Netherlands; University of Groningen, the Netherlands; subspecies P.p. pica.
JACKDAW
IDENTIFICATION: A small crow with black plumage and gray on the back of the head. DISTRIBUTION: Eurasia, North Africa. HABITAT: Forest, grassland, farmland. STUDY AREAS: Haren, the Netherlands; Max-Planck Institute; subspecies C.m. spermologus.
RAVEN
IDENTIFICATION: A large (2 foot), all-black bird similar to a crow but much bulkier. DISTRIBUTION: Eurasia, North America. HABITAT: Varied, including forest, plains, desert. STUDY AREA: Max-Planck Institute; subspecies C.c. corax.
Social Organization
All three of these Crow species are quite gregarious, often associating in flocks and communal roosts. Individuals generally form long-term mated pairs, and Jackdaws usually nest in colonies. Magpies sometimes participate in remarkable group displays known as CEREMONIAL GATHERINGS, noisy aggregations that may be related to territory acquisition.
Description
Behavioral Expression: Black-billed Magpies sometimes court and form pair-bonds with birds of the same sex. Partners include adult males with younger or juvenile males (less than one year old), or else two females or two males of the same age, usually juveniles but also sometimes two adult males. A typical homosexual courtship—for example, between two males—begins with one bird ritually BEGGING the other by crouching in front of him and flapping or quivering his wings while uttering a begging call. The other male responds by hopping in tight circles around him, fluffing up his white feathers and flicking his wings; he may also BABBLE-SING, a varied combination of warbling, chattering, and yelping notes. The circling male often adopts a TILTING posture, in which he points his head and tail sideways toward the other male. If the male he is courting flies off, a courtship pursuit known as CHASE-HOPPING may develop, in which one male follows the other while alternately flying and hopping. Sometimes the two birds also HOVER-FLY, one in front of the other, using a rhythmic, undulating flight pattern. The same series of behaviors is seen in courtships between females (as well as in heterosexual interactions). Homosexual courtship sessions can last for up to half an hour. After courting, two birds of the same sex may form a pair-bond. Paired birds stay near each other, follow one another, and often cooperate in evicting intruders from their territory. They also frequently sit close together and preen one another or engage in mutual BILLING, in which they affectionately nibble at each other’s beak. Sometimes, homosexual mates also pull or nibble on the same leaf or twig and pass it back and forth between them; this is known as TUGGING. Same-sex pair-bonds are generally of shorter duration than adult heterosexual bonds and last from a few days to several months. However, adult males sometimes form longer-lasting homosexual pairs, and the two birds may even build a nest together (which typically takes five to seven weeks to construct).
Female Jackdaws occasionally develop pair-bonds with other females. In some cases, an older female pairs with a younger one, and the two build a nest together even though the juvenile bird is too young to lay eggs. Later, they might construct a unique “double nest” consisting of two adjacent cups and lay infertile eggs in both cups. Sometimes, a homosexual pair is joined by a male, who may bond with one or both of the females to form a bisexual trio; in this way, the females can lay fertilized eggs. However, they are often unable to successfully care for their offspring, precisely because their bond to each other means that they try to stay together all the time. The two females incubate their eggs and brood their youngsters simultaneously, each sitting on one cup. When the male arrives for his shift, however, they both depart together, leaving the male to try to cover and protect both sets of eggs or nestlings at the same time (which he is usually unable to do). Sometimes, a bi-sexual trio forms when a female joins a heterosexual pair and develops a strong bond with the female partner. The two females engage in courtship and pair-bonding activities such as mutual preening or COURTSHIP-FEEDING, in which one partner begs the other by crouching, fluttering her wings, and quivering her tail. Both females might mate with the male and lay fertile eggs, although the bond between them can end up being stronger than the original heterosexual bond. In fact, in one case the female partners were not able to properly care for their young because the male denied the female “interloper” access to the nestlings. Homosexual bonds also sometimes develop between widowed and nonbreeding females. In these cases, females that lose their male partners during the breeding season may attract unmated females to pair with them; some of these widows are mothers, while others have no offspring. Unlike bisexual trios, which may remain together for years, these female bonds appear to be more transitory, usually lasting only for several weeks until the breeding season is over.
Homosexual courtship in Black-billed Magpies: “tilting” (left) and “begging”
Female homosexual pairs also occasionally occur in Ravens, including incestuous bonds between yearling sisters. Birds in same-sex pairs engage in intense courtship activity similar to heterosexual pairs, such as mutual preening and courtship-feeding.
Frequency: Among Jackdaws in the wild, approximately 5 percent of trios include bonding between the two female partners, while about 10 percent of widowed females form homosexual pairs. Overall, though, same-sex bonds probably represent no more than 1 percent of all pairs/trios. Homosexual activity occurs sporadically in Black-billed Magpies and Ravens as well: about 1 percent of nesting pairs of Magpies, for example, consist of two males. Although homosexual copulations between Magpies have not yet been recorded, heterosexual matings are also infrequently observed (only 9 male-female copulations, for example, were recorded during one 300—hour study period).
Orientation: Homosexual behavior is most prevalent among younger Black-billed Magpies, some of whom also court members of the opposite sex; many of these birds go on to form heterosexual attachments when they become adults, but most are nonbreeders during the time of their same-sex activities. Some adult males, however, continue to court younger males or pair with other adult males. In Jackdaws and Ravens many different forms of bisexuality occur. Some females are simultaneously bonded to both males and females, and such trios may develop out of either an initial heterosexual or homosexual pair-bond. Some females are sequentially bisexual, developing same-sex bonds only after losing their male partners. However, those Jackdaw females who enter into homosexual pairs as nonbreeders may have no prior (and perhaps no subsequent) heterosexual experience.
Nonreproductive and Alternative Heterosexualities
Black-billed Magpies and Jackdaws participate in a number of nonprocreative heterosexual activities. Birds sometimes copulate long after fertilization has taken place—even during incubation or chick-rearing—while courtship and mounting may occur well in advance of the breeding season in Magpies. In both species, birds form pair-bonds as juveniles, long before they are able to breed. Several alternatives to the monogamous pair and nuclear family are also to be found in these species of Crows. In Black-billed Magpies, for example, courtship and copulations with birds outside of the pair-bond can be more frequent than within-pair matings. In addition, some pairs get divorced: about half of all males and just under two-thirds of females change mates, and some may pair with up to three different partners over the course of their lives. Other Magpies, however, do remain in lifelong, faithful pair-bonds. About 6—10 percent of adult Jackdaw pairs, and a third of all juvenile pairs, get divorced. Polygamous trios also sometimes develop in Magpies (1—2 percent of bonds), but are fairly common in Jackdaws, comprising about 14 percent of all bonds. These usually result from an unpaired female joining an existing male-female pair; unlike the bisexual trios described above, she usually bonds only with the male of the pair, not the female. Occasionally, she may oust the former female and start a new family with the male; frequently, however, the newcomer female does not breed even if she remains in the trio for several years.
Nonbreeding couples also occur in Jackdaws and Ravens, as well as a significant population of single, nonreproducing birds. The latter are found in Magpies as well, where they make up 20—60 percent of the population and may be solitary or form their own flocks. In addition, about half of all Magpies that survive to adulthood leave no descendants (even if they try to breed). Some nonbreeding Jackdaw pairs—or couples who have tried unsuccessfully to breed—end up harassing breeding pairs by invading their nests, fighting with them, and even attacking and occasionally killing their young with vicious pecks. Nearly a third of all breeding pairs in some populations are harassed in this way. Cannibalism of young and eggs by neighboring breeding pairs also sometimes occurs in Jackdaws. Magpies and Ravens occasionally adopt unrelated youngsters when they pair with a bird that has lost its mate. Magpie families also sometimes foster-parent chicks as a result of the extraordinary phenomenon of “egg transfer”: in some populations, up to 8 percent of nests contain a foreign Magpie egg, but not as a result of being laid there. Rather, another Magpie has physically carried its own egg in its beak to the new nest, placing it there to hatch and be raised by the host parents. Stealing and cannibalism of young or eggs has also been reported among Black-billed Magpies: about 7 percent of nests are robbed by other Magpies. In addition, at least 30 percent of nestlings die of starvation as a result of competition from their siblings, or from direct attacks or cannibalism by their nest-mates.
Other Species
Homosexual courtship occurs in some species of Jays (closely related to Crows), so far observed only in captivity. Male Gray-breasted or Mexican Jays (Aphelocoma ultramarina), a species found in the American Southwest and Mexico, have been seen COURTSHIP-FEEDING younger males in mixed-sex groups. This behavior—also part of heterosexual courtships—involves one male offering the other a food item; the latter accepts it while quivering his wings, crouching, and uttering a low kwa kwa kwa call. After eating the food or storing it in a cache, he may follow the other male to repeat the episode. Female San Bias Jays (Cyanocorax san-blasianus) of Mexico have been known to court other females in same-sex groups in captivity, using the SOTTO VOCE SONG DISPLAY. While making soft, throaty vocalizations, one female sidles up to the other on a perch with her tail raised and belly feathers fluffed.
Sources
*asterisked references discuss homosexuality/transgender
Antikainen, E. (1981) “The Breeding Success of the Jackdaw Corvus monedula in Nesting Cells.” Ornis Fennica 58:72–77.
*Baeyens, G. (1981a) “Magpie Breeding Success and Carrion Crow Interference.” Ardea 69:125–39.
———(1981b) “Functional Aspects of Serial Monogamy: The Magpie Pair-Bond in Relation to Its Territorial System.” Ardea 69:145–66.
*———(1979) “Description of the Social Behavior of the Magpie (Pica pica).” Ardea 67:28–41.
Birkhead, T. (1991) The Magpies: The Ecology and Behavior of Black-billed and Yellow-billed Magpies. London: T. and A. D. Poyser.
Birkhead, T., and J. D. Biggins (1987) “Reproductive Synchrony and Extra-Pair Copulation in Birds.” Ethology 74:320–34.
Birkhead, T., S. F. Eden, K. Clarkson, S. F. Goodburn, and J. Pellatt (1986) “Social Organization of Magpies Pica pica.” Ardea 74:59–68.
Buitron, D. (1988) “Female and Male Specialization in Parental Care and Its Consequences in Black-billed Magpies.” Condor 90:29–39.
———(1983) “Extra-Pair Courtship in Black-billed Magpies.” Animal Behavior 31:211-20.
Coombs, F. (1978) The Crows: A Study of the Corvids of Europe. London: B. T. Batsford.
Dhindsa, M. S., and D. A. Boag (1992) “Patterns of Nest Site, Territory, and Mate Switching in Black-billed Magpies (Pica pica).’ Canadian Journal of Zoology 70:633–40.
Dunn, P O., and S. J. Hannon (1989) “Evidence for Obligate Male Parental Care in Black-billed Magpies.” Auk 106:635–44.
*Hardy, J. W. (1974) “Behavior and Its Evolution in Neotropical Jays (Cissilopha).” Bird-Banding 45:253–68.
*———(1961) “Studies in Behavior and Phylogeny of Certain New World Jays (Garrulinae).” University of Kansas Science Bulletin 42:13–149.
Jerzak, L. (1995) “Breeding Ecology of an Urban Magpie Pica pica Population in Zielona Góra (SW Poland).” Acta Ornithologica 29:123–33.
*Lorenz, K. (1972) “Pair-Formation in Ravens.” In H. Friedrich, ed., Man and Animal: Studies in Behavior, pp. 17–36. New York: St. Martin’s.
*———(1935) “Der Kumpan in der Umwelt des Vögels.” Journal für Ornithologie 83:10–213, 289–413. Reprinted as “Companions as Factors in the Bird’s Environment.” In K. Lorenz (1970) Studies in Animal and Human Behavior, vol.1, pp. 101–258. Cambridge, Mass.: Harvard University Press.
Ratcliffe, D. (1997) The Raven: A Natural History in Britain and Ireland. London: T. and A. D. Poyser.
Reynolds, P. S. (1996) “Brood Reduction and Siblicide in Black-billed Magpies (Pica pica).” Auk 113:189–99.
*Röell, A. (1979) “Bigamy in Jackdaws.” Ardea 67:123–29.
———1978) “Social Behavior of the Jackdaw, Corvus monedula, in Relation to Its Niche.” Behavior 64:1–124.
Trost, C. H., and C. L. Webb (1986) “Egg Moving by Two Species of Corvid.” Animal Behavior 34:294–95.
BIRDS OF PARADISE, BOWERBIRDS, AND OTHERS
RAGGIANA’S BIRD OF PARADISE
IDENTIFICATION: A crow-sized bird; male has a bright yellow head, an iridescent green throat, and a long “tail” of orange flank feathers; female has a duller yellow head and brown facial mask and no orange “tail.” DISTRIBUTION: Southern and northeastern Papua New Guinea. HABITAT: Lowland and hill forests. STUDY AREA: In captivity at the Baiyer River Sanctuary, Mt. Hagen, Papua New Guinea; subspecies P.r. augustaevictoriae.
VICTORIA’S RIFLEBIRD
IDENTIFICATION: Adult males are black with an iridescent sheen and metallic crown, throat, and central tail feathers; females and younger males are drabber, with brown, buff, and off-white plumage. DISTRIBUTION: Northeast Queensland, Australia. HABITAT: Rain forest, eucalyptus forest, swamp woodlands. STUDY AREAS: Southern Atherton Tableland, Queensland, Australia, including near Townsville and in the Ingham and Palmerston National Parks.
Social Organization
Male Raggiana’s Birds of Paradise perform courtship displays on communal “courts” or LEKS (located in tree branches) in groups of up to eight individuals at a time; females visit the leks in pairs or small groups. Male Victoria’s Riflebirds display singly. Both species have a polygamous or promiscuous mating system, in which males copulate with more than one female but do not participate in any parental duties.
Description
Behavioral Expression: Male Victoria’s Riflebirds sometimes court younger males with a series of spectacular displays (also seen in heterosexual courtships). Adult males attract individuals of both sexes to their display perches by repeatedly calling with a loud yass note and opening their bills to expose the bright yellow mouth interior. When an interested male (or female) approaches, the courting male begins his CIRCULAR WINGS AND GAPE display, in which he fans his wings to form a perfect circle with the tips meeting above his head while simultaneously raising and lowering his body. The wing circle is held vertically as he gapes his bill and presents his iridescent throat feathers to the other male. If the latter lands on the display perch, the courtship progresses to its final phase, the astounding ALTERNATE WINGS CLAP display. The adult male begins swaying and twisting his body from side to side, alternately raising and lowering each wing so that they “clap” with a dull, thudding sound when they meet above his head. Gradually the wings are brought forward while being clapped so that they encircle the younger male. The tempo of the display is increased until, at its climax, the wing-clapping reaches an astounding speed—each wing alternately encircles the observing male at a rate approaching twice a second. The courted male becomes mesmerized by the brilliant metallic bluish green throat shield of the displaying male as it is jerked violently back and forth, and he may respond by simultaneously performing his own alternate wings clap display. If both males are displaying, they alternate wing movements, gradually crouching while arching their heads back and quivering all over. They often perform several bouts of mutual display with brief rests between each. Occasionally one male briefly mounts the other; full copulation does not usually occur, though, since the mounted male often simply flies away from underneath the male mounting him.
Courtship displays between female Raggiana’s Birds of Paradise involve some of the same postures and movements used in heterosexual courtship in this species. One female arches her wings above her back and then claps them against her sides, all the while bobbing up and down and erecting the feathers on her back and flanks as she dances in front of the other female. Every now and then she makes an ur, ur call, and she may even hang upside down on a branch while flicking her wings and calling. This dramatic pose is held for a minute or more at a time. Males use this inverted posture to show off their orange “tail” plumes during courtship, but females perform this display even though they do not have such ornate feathers. Sometimes two females engage in mutual display, facing each other while holding their wings stiffly above their backs and bobbing.
A male Victoria’s Riflebird courting another male with the “circular wings and gape” display
Frequency: Courtship displays between male Victoria’s Riflebirds occur fairly often at some times of the year, especially during the postmolting period in February and March. Although homosexual mountings are not common in this species, opposite-sex matings have in fact been seen only a few times during more than a hundred courtship displays observed in the wild.
Orientation: At least some male Victoria’s Riflebirds are functionally bisexual, courting and attempting to mate with both males and females. In Raggiana’s Bird of Paradise, courtship display between females has so far only been observed in captivity in the absence of males, so this behavior may be the expression of a potential or “latent” bisexual capacity. More detailed field observations and life histories are required, though, before any definitive statements can be made regarding the sexual orientation of individuals that engage in this activity.
Nonreproductive and Alternative Heterosexualities
Only about 11 percent of lek visits by female Raggiana’s Birds of Paradise actually result in heterosexual mating. More often than not, a courtship interaction is broken off by a female before copulation occurs. In addition, males often chase females and behave aggressively toward them on the lek, which deters them from participating in sexual interactions. When mating does take place, the female often mounts the male prior to copulation. Such REVERSE mounts are then followed by a display in which the male appears to pummel his partner with his wing. The female crouches on her perch absorbing the blows for 20—35 seconds, after which copulation occurs. Nonreproductive matings also take place outside of the breeding season. Many males may delay breeding up to five or more years once becoming sexually mature, since they do not generally acquire their ornate plumage (used in courtship displays) for several years.
Other Species
Male Greater Birds of Paradise (Paradisaea apoda), a species closely related to Raggiana’s, also sometimes court and mount younger males.
Sources
* asterisked references discuss homosexuality/transgender
Beehler, B.M. (1989) “The Birds of Paradise.” Scientific American 261(6):116–23.
———(1988) “Lek Behavior of the Raggiana Bird of Paradise.” National Geographic Research 4:343–58.
*Bourke, P. A., and A. F. Austin (1947) “The Atherton Tablelands and Its Avifauna.” Emu 47:87–116.
Davis, W. E., Jr., and B. M. Beehler (1994) “Nesting Behavior of a Raggiana Bird of Paradise.” Wilson Bulletin 106:522–30.
*Frith, C. B. (1997) Personal communication.
———(1981) “Displays of Count Raggi’s Bird-of-Paradise Paradisaea raggiana and Congeneric Species.” Emu 81:193–201.
*Frith, C. B., and W. T. Cooper (1996) “Courtship Display and Mating of Victoria’s Riflebird Ptiloris victoriae with Notes on the Courtship Displays of Congeneric Species.” Emu 96:102–13.
Frith, C. B., and D. W. Frith (1995) “Notes on the Nesting Biology and Diet of Victoria’s Riflebird Ptiloris victoriae.” Emu 95:162–74.
Gilliard, E. T. (1969) “Queen Victoria Rifle Bird” and “Count Raggi’s Bird of Paradise.” In Birds of Paradise and Bower Birds, pp. 112–17,222–29. Garden City, N.Y.: Natural History Press.
Lecroy, M. (1981) “The Genus Paradisaea—Display and Evolution.” American Museum Novitates 2714:1–52.
*Mackay, M. (1981) “Display Behavior by Female Birds of Paradise in Captivity.” Newsletter of the Papua New Guinea Bird Society 185/186 (November-December):5.
IDENTIFICATION: A thrush-sized bird (12 inches) with velvety black plumage and brilliant golden yellow crown, nape, upper back, and wing feathers. DISTRIBUTION: East-central Australia. HABITAT: Humid forests. STUDY AREA: Sarabah Range, Queensland, Australia.
Social Organization
Regent Bowerbirds have a polygamous or promiscuous mating system: males court and mate with multiple partners on display territories (see below). Following the mating season birds often associate in cosexual flocks of 10—20 individuals.
Description
Behavioral Expression: Male Regent Bowerbirds build elaborate structures called BOWERS, in which they court both males and females. Bowers built by adult males form an “avenue” on the ground consisting of two parallel walls of twigs—10—12 inches high and 7—8 inches long—which are inserted into a platform of twigs on the ground. In some bowers the walls form a sort of arched walkway, while other bowers have triangular-shaped walls of different sizes. The bower is usually decorated with a dozen or so “display objects” or ornaments that are often selected for their color and strewn on the platform. These include brown snail shells, berries, green or purplish leaves, brown fruits and seeds, cicada husks, occasionally a yellow or pink flower petal, and even scavenged pieces of blue plastic. Remarkably, some birds also “paint” the walls of their bowers by applying, with their bills, macerated plant material mixed with saliva, giving some of the twigs a yellowish green coating. Adult males display in their bowers to females and younger males by flicking their wings and bowing their heads to show off their brilliant orange and yellow neck feathers. Sometimes they also ritually “present” display objects to the bird they are courting by picking up one of the ornaments from the avenue and holding it in their bill while facing their partner.
A bower constructed by a male Regent Bowerbird, used during courtship displays to both males and females
Juvenile males also build bowers and court both males and females. In some cases, they use the same bower shapes and displays as adults, but in other cases they utilize their own patterns, some of which may be unique to same-sex interactions. Some bowers built by younger males are more in the form of a horseshoe—open only at one end—with the sticks woven horizontally rather than vertically. When courtship-displaying to an adult male, the younger male enters the bower and squats with his tail toward the entrance. The adult male then rushes toward the juvenile, who is behind the closed end of the bower, or sometimes goes around to the entrance and tweaks the younger male’s tail. When courting other juvenile birds of both sexes, young males may perform a dance in the center of the bower, picking up an ornament and bobbing up and down with half-opened wings, then tossing the object over the bower wall. The bird(s) watching this display sweep and brush the ground with their wings.
Many younger males are transvestite, having a plumage coloration that more closely resembles that of adult females than adult males. It takes males up to seven years to develop the full yellow, orange, and black feathers typical of adult males, and during that time many actually exhibit plumages that are intermediate between the adult male and female patterns.
Frequency: Among adult male Regent Bowerbirds, 15 percent of their bower courtship time is spent displaying to other males, while 28 percent of juvenile males’ display time is same-sex.
Orientation: Regent Bowerbirds that court other males are probably bisexual, since they display to birds of both sexes.
Nonreproductive and Alternative Heterosexualities
A large segment of the male Regent Bowerbird population is nonbreeding: only about a third of all adult males maintain bowers, and of those that do, only a fraction actually mate with females. In addition, heterosexual courtship interactions rarely result in copulation: in only about 7 percent of female visits to bowers does mating actually take place, since the female often leaves while the male is displaying (and in 10 percent of female visits the male does not display at all).
Other Species
Adult male Satin Bowerbirds (Ptilonorhynchus violaceus) from Australia have also been observed performing courtship displays toward younger males.
Sources
*asterisked references discuss homosexuality/transgender
Chaffer, N. (1932) “The Regent Bird.” Emu 32:8–11.
*Gilliard, E. T. (1969) “Australian Regent Bower Bird.” In Birds of Paradise and Bower Birds, pp. 335–44. Garden City, N.Y.: Natural History Press.
Goddard, M. T. (1947) “Bower-Painting by the Regent Bower-bird.” Emu 47:73–74.
*Lenz, N. (1994) “Mating Behavior and Sexual Competition in the Regent Bowerbird Sericulus chrysocephalus.” Emu 94:263–72.
*Marshall, A. J. (1954) “Satin Bower-bird, Ptilonorhynchus violaceus (Vieillot)” and “Regent Bower-bird, Sericulus chrysocephalus (Lewin).” In Bower-birds: Their Displays and Breeding Cycles, pp. 26–71, 109–18. Oxford: Oxford University Press.
*Phillipps, R. (1905) “The Regent Bird (Sericulus melinus).” Avicultural Magazine (new series) 4:51—68, 88—96, 123—31.
Plomley, K. F. (1935) “Bower of the Regent Bower-bird.” Emu 34:199.
IDENTIFICATION: A pheasant-sized bird with brownish gray plumage, powerful legs and claws, and long, ornate tail feathers. DISTRIBUTION: Southeastern Australia. HABITAT: Rain forest, eucalyptus, other forests. STUDY AREAS: Sherbrooke Forest near Melbourne, Australia; Adelaide Zoo, South Australia.
Social Organization
Adult male Superb Lyrebirds establish territories on which they build earth mounds three to five feet wide, used as platforms for courtship displays. The mating system is polygamous or promiscuous: birds mate with multiple partners without developing long-lasting pair-bonds, and males do not contribute to raising their offspring. Adolescent Lyrebirds often associate in small groups, sometimes consisting only of males.
Description
Behavioral Expression: Male Superb Lyrebirds often court younger (adolescent) males on encountering them either in their groups or singly. The adult male closely follows the younger male, sometimes for hours at a time, periodically performing the WING-RAISING DISPLAY, in which he lifts and fans one wing toward his partner. With neck outstretched, he serenades the other male with a variety of extraordinary vocalizations, such as “whisper-song”; chortling; a call that can be rendered phonetically as clonk clonk clickety clickety click; another vocalization that sounds like the grinding of a pair of scissors; as well as uncanny imitations of other birds’ songs. Sometimes the courtship progresses to spectacular displays of the male’s elongated and stunningly beautiful tail feathers. In the dazzling FULL-FACE DISPLAY, for example, the older male arches his tail forward over his head and spreads the silvery filamentary feathers, hiding his body behind a gossamer fan framed by the elegant lyre-shaped, chestnut-striped outer tail feathers (for which the bird is named). Often the entire tail is vibrated to create a shimmering effect directed toward the other male. This may be followed by the INVITATION DISPLAY, in which the male almost “closes up” his quivering tail fan while still holding it forward (the feather tips almost touching the ground in front of him), all the while repeating a blick blick blick call. Occasionally, the younger male being courted by an adult is his own offspring. Adult males also sometimes mount adolescent males, even during the nonbreeding season when the adult bird is molting and has shed his elaborate tail plumes. Genital contact probably does not occur, though, since the younger male usually does not facilitate the interaction.
An adult male Superb Lyrebird (with molted tail feathers) mounting a younger male in Australia
Adolescent male Lyrebirds also sometimes mount one another as well as particpate in homosexual courtship displays. Courtship between younger males is usually mutual, with both birds singing and displaying to one another. Occasionally an adult and an adolescent male also engage in mutual display, and adult females (in captivity) have been observed performing a similar courtship display to each other. Typically, the two adolescent males circle around each other on a display mound, tails raised in a fan shape with their feathers intermingled and beaks nearly touching while performing a vocal duet. One male may also perform a full-face or invitation display, and his partner sometimes runs underneath his outstretched tail the way a female does during heterosexual courtship. Sometimes the two males engage in what appears to be a form of COURTSHIP-FEEDING: in response to begging from his partner, one male regurgitates a worm or other food item as an offering to the other, who promptly eats it. This behavior appears to be unique to homosexual courtships. Two younger males often form a “companionship”: in addition to courting each other, they follow one another, feed together (even digging in the same hole for food items), roost next to each other, and share bathing pools. These male pair-bonds usually last for only a few days, and adolescent males often form multiple serial attachments of this sort.
Two younger male Superb Lyrebirds performing a mutual courtship display
Frequency: Homosexual courtship occurs fairly often in Superb Lyrebirds. Adult males approach groups of adolescent males approximately once every three days during the breeding season and roughly once every day and a half outside the breeding season, and 93 percent of these encounters include courtship. In comparison, heterosexual encounters occur about four times as often as homosexual encounters during the breeding season, and about twice as often outside the breeding season. Adult males associate with adolescent males (in groups or singly) more than half of the time they are away from their display mounds. Same-sex mounting occurs less frequently than courtship interactions between males.
Orientation: Most adult males are functionally bisexual, courting and mounting both females and younger males. Adolescent males appear to be more exclusively homosexual: most individuals form same-sex companionships and engage in homosexual courtship (and sometimes mounting) for several years prior to mating heterosexually. Some females probably have a bisexual potential that manifests itself in the absence of males (for example, in captivity).
Nonreproductive and Alternative Heterosexualities
Male and female Superb Lyrebirds lead largely separate lives. Other than brief encounters during the breeding season for courtship and copulation, the two sexes rarely interact: only about 8—10 percent of all Lyrebird sightings are of males and females together. Because males do not contribute at all to parenting, incubation and chick-raising often become burdensome for females—and by extension, potentially harmful for the eggs and/or chicks. During the early stages of incubation, females regularly leave their eggs unattended during the day for up to seven hours at a time to feed, causing the egg temperature to drop dramatically. Overall, females are relatively “inattentive” parents, incubating their eggs for only about 27—45 percent of the available daylight hours; this is significantly less than in other perching birds, who generally spend 60—80 percent. Because the eggs are laid and incubated during the coldest months of winter, they are consequently exposed to dangerously low (sometimes even sub-freezing) temperatures that generally slow embryonic development. After hatching, nestlings occasionally die from overexposure when their mother has been away from the nest for too long.
Sources
*asterisked references discuss homosexuality/transgender
Kenyon, R. F. (1972) “Polygyny Among Superb Lyrebirds in Sherbrooke Forest Park, Kallista, Victoria.” Emu 72:70—76.
Lill, A. (1986) “Time-Energy Budgets During Reproduction and the Evolution of Single Parenting in the Superb Lyrebird.” Australian Journal of Zoology 34:351—71.
*———(1979a) “An Assessment of Male Parental Investment and Pair Bonding in the Polygamous Superb Lyrebird.” Auk 96:489—98.
———(1979b) “Nest Inattentiveness and Its Influence on Development of the Young in the Superb Lyrebird.” Condor 81:225—31.
Reilly, P. (1988) The Lyrebird: A Natural History. Kensington, Australia: New South Wales University Press.
*Smith, L. H. (1996-97) Personal communication.
*———(1988) The Life of the Lyrebird. Richmond, Australia: William Heinemann.
(1982) “Molting Sequences in the Development of the Tail Plumage of the Superb Lyrebird, Menura novae-hollandiae.” Australian Wildlife Research 9:311—30.
*———(1968) The Lyrebird. Melbourne: Lansdowne Press.
Watson, I. M. (1965) “Mating of the Superb Lyrebird, Menura novae-hollandiae.” Emu 65:129—32.
Other Birds
FLIGHTLESS BIRDS
OSTRICH
IDENTIFICATION: The largest living bird (over 6 feet tall), with striking black-and-white plumage in the male and powerful legs and claws. DISTRIBUTION: Southern, eastern, and west-central Africa. HABITAT: Open savanna, dry veld, steppe, semidesert. STUDY AREA: Namib Game Reserve, Namibia; subspecies S.c. australis, the South African Ostrich.
EMU
IDENTIFICATION: The second-largest living bird (5—6 feet tall), with shaggy, brown plumage and bare patches of blue skin on the face and neck. DISTRIBUTION: Australia. HABITAT: Arid plains, semidesert, scrub, open woodland. STUDY AREAS: Barcoo River and Alice Downs areas, Central Queensland, Australia; Division of Wildlife Research, Helena Valley, Western Australia; Berlin Zoo and Melbourne Zoological Gardens.
GREATER RHEA
IDENTIFICATION: Similar to Ostrich but smaller (up to 41/2 feet tall) and with overall grayish brown plumage in both sexes. DISTRIBUTION: Southeastern South America. HABITAT: Open brush, grassland, plains. STUDY AREA: Near General Lavalle, Buenos Aires Province, Argentina; subspecies R.a. albescens.
Social Organization
Ostriches associate in flocks and frequently form sex-segregated groups. All-male flocks may contain up to 40 individuals, many of them juveniles, who travel with each other for long periods. Emus generally associate in pairs or groups of 3—10 birds, while Greater Rheas gather in flocks of 15—40 birds outside of the mating season. All three species have a wide variety of mating systems (discussed below). These are notable for their various forms of POLYANDRY (females mating with several males) and the fact that—in Emus and Greater Rheas—all incubation and chick-rearing is performed by males without any help from females.
Description
Behavioral Expression: Male Ostriches perform a homosexual courtship dance to each other that is distinct from heterosexual interactions. Same-sex courtships consist of a sequence of three activities, performed by sexually mature adult males in full nuptial plumage (black-and-white feathers, with a red flush on the face and legs). First, there is a dramatic APPROACH in which one male runs rapidly toward his chosen partner—often achieving speeds of 25—30 mph—and stops abruptly just short of the other male. Then he launches into frenzied PIROUETTE DANCING, a high-speed, energetic circling in place beside his partner. This whirling may occur in a series of bursts, each lasting for several minutes. Finally, in KANTLING, the male drops to the ground next to his partner and rocks steadily from side to side, fluffing out his tail and sweeping the ground with his wings in an exaggerated fashion. All the while, he twists his head and neck in a continuous corkscrew action and repeatedly inflates and deflates his throat. The male being displayed to may acknowledge the dance with his posture, or he may simply maintain a calm stance devoid of alarm or aggression. Homosexual courtships are distinct from heterosexual ones in a number of respects: neither the running approach nor pirouette dancing occur in male-female interactions. Kantling is performed in heterosexual contexts but differs because it is usually accompanied by singing (when males display to females, they frequently produce a booming call), and it is significantly shorter. Same-sex displays last for 10—20 minutes, while opposite-sex ones rarely exceed three minutes. Also, symbolic feeding and nest-site displays are components of heterosexual but not homosexual courtships.
A male Ostrich (right, on the ground) courting another male with the “kantling” display
Although no copulation takes place between courting male Ostriches, homosexual mating has been observed in pairs of male Emus. A sexual interaction begins with one male approaching the other, stretching his neck upward and erecting his neck feathers so that they stand out horizontally, while grunting deeply. The two birds begin following and chasing each other; if the male who initiated the activity is behind the other, he may make treading movements with his feet, indicating his intention to mount the other. Often, however, it is the initiating male who lies flat on the ground as an invitation for the other male to mount. The males may also take turns mounting each other. The mounting male lies down behind his partner, resting his breast on the other’s rump, and uses his heels to slide forward until he covers most of the other male. While copulation is taking place, the mountee makes soft grunting noises (not usually heard during heterosexual matings), and the mounter gently toys with the feathers on his partner’s upper back. After mating, his erect penis is often visible: the male Emu, along with other ratites, is one of the few birds in the world that has a penis (most male birds simply have a cloacal, or genital, opening).
Joint parenting in male Greater Rheas: two males in Argentina (above) sitting on their double nest, which contains two sets of eggs (below) that are frequently rolled between the coparents
Male Emus also sometimes coparent with each other: two (and occasionally three) males may attend one nest at the same time, incubating all the eggs together. Such nests often contain SUPERNORMAL CLUTCHES of 14—16, and sometimes more than 20, eggs. This is over twice the number found in nests attended by single males, probably because more than one female has laid in them. Unlike single fathers, male coparents are able to take a break from incubating while their partner sits on the nest; they also sometimes roll the eggs between them while on the nest together. Although they are probably not sexually involved with one another, the two fathers cooperate in raising their chicks together, calling to them with “purr-growls” and jointly defending them from predators. A similar phenomenon is found in Greater Rheas: pairs of males occasionally sit on “double nests” that are close to or touching one another; they incubate the eggs together and jointly parent the chicks when they hatch. Most such nests begin as standard nests with only one male incubating, after which another male joins him and begins transferring eggs to his half of the nest; later, eggs may be transferred back and forth between the twin nests. Unlike Emu nests belonging to male coparents, Rhea double nests usually have a combined number of eggs that is the same as for single nests. Male coparents are different from male nest helpers, which are also found in Rheas. About a quarter of breeding males are assisted by an adolescent male, who incubates and raises (on his own) a clutch of eggs fathered by the adult while the latter goes off to start a new family. This differs from male coparenting in that the two nests are widely separated from one another, each contains the full clutch size of a single nest, the two males never share parenting duties, and the helper is always an adolescent male.
Female Ostriches are occasionally transvestite, having full black-and-white male plumage (along with underdeveloped ovaries).
Frequency: Homosexual courtship in Ostriches is quite common in some populations, occurring two to four times a day (usually in the morning). Sexual behavior between male Emus has so far only been observed in captivity, but it does occur repeatedly between partners. Among Greater Rheas, joint parenting between males occurs in about 3 percent of all nests; Emu coparenting probably occurs at a similar rate.
Orientation: In Ostriches, 1—2 percent of all adult males engage in homosexual courtship in some populations. Male Ostriches who court other males typically ignore any females that may be present; they are probably solitary birds that participate in little, if any, heterosexual interactions. Most Emus and Rheas that participate in male coparenting have probably mated and/or paired with females earlier in the season prior to parenting with another male. Male Emus may also have a latent capacity for bisexuality, as evidenced by the occurrence of sexual behavior between captive males (at least one of whom had previously mated heterosexually). However, individual life histories and the full patterns of sexual orientation have not yet been systematically studied in this species.
Nonreproductive and Alternative Heterosexualities
Heterosexual mating in Ratites occurs in the context of an extraordinary variety of complex social arrangements that deviate significantly from the nuclear-family model. Ostriches have a mating system that has been described as SEMIPROMISCUOUS MONOGAMY. Male and female Ostriches form a type of pair-bond with each other that one biologist describes as a sort of “open marriage,” since both partners also copulate with a number of other birds besides their primary partner (birds often mate with a different primary partner each year as well). In addition, females often lay eggs in nests other than their own, especially if they are not the primary partner of a male. As a result, many of the eggs that a pair incubates (and the young they raise) are not necessarily their own. Adoption also occurs when broods are combined to form nursery groups or CRÈCHES—sometimes containing hundreds of chicks—that are looked after by one or more adults. Emus utilize SERIAL POLYANDRY in their mating system: a male pairs with one female who remains with him until incubation begins, at which point the female leaves her partner and pairs with a new male to begin a second clutch. Many females also seek nonmonogamous matings, copulating with males other than their pair-mate. One study found that the majority of copulations—nearly three-quarters—are promiscuous. In addition, copulation between pair members may be nonprocreative, occurring several months before egg laying. Greater Rheas have a variable mating system that can be characterized as SERIAL POLYGYNANDRY: a male associates with a “harem” of three to ten females, all of whom he mates with. The females lay their eggs communally in one nest; after the male begins to incubate, the females then move on to another male, repeating the process with up to seven different males. As noted above, most Emu and Rhea males are single parents, which can be an arduous task. While tending the eggs, male Rheas rarely leave the nest for more than a few minutes during the six-week incubation period. Male Emus often become severely emaciated and weakened from not eating, drinking, defecating, or leaving the nest during their entire eight-week incubation period. Nonbreeding and failed breeding attempts also occur at high rates among Greater Rheas: less than 20 percent of males even try to reproduce each year, and overall only 5—6 percent of males are successful at breeding each year.
As discussed above, sex-segregated flocks are common among Ostriches, many of whom are not involved in heterosexual pursuits. Also, heterosexual courtship is often not synchronized: females typically begin approaching males several weeks before the latter become sexually interested, and during this time the males often appear to ignore or be indifferent to the females’ advances. The onset of the males’ sexual cycle is marked by a red flush on the legs and face, as well as enlargement and erection of the penis, which is often displayed in a special “penis-swinging” ceremony. However, once males begin courting, nearly a third of their advances are, in turn, refused by females. Among Emus and Rheas, outright hostility often develops between the sexes once the male starts incubating. Fathers typically threaten, chase, or attack females that try to approach them, while female Emus have been seen responding with vicious double-footed kicks that can tumble males head over heels. Infanticide also sometimes occurs: females that are able to get close to a male tending his chicks may end up killing the youngsters. Egg abandonment or destruction takes place among Ostriches, often of eggs laid by another female. Abandonment also occurs in Greater Rheas, where nearly two-thirds of nests are deserted by males during incubation. In addition, female Rheas who are unable to find a nest and male caretaker for their eggs often lay them in the open and then abandon them; these are known as ORPHAN EGGS. Once (nonorphan) eggs hatch, fathers often adopt youngsters from other broods, raising them alongside their own. Nearly a quarter of male Rheas are adoptive parents, and up to 37 percent of each of their broods may be composed of foster chicks. Researchers have found that adopted young actually have a better chance of surviving than do their stepsiblings.
Sources
*asterisked references discuss homosexuality/transgender
Bertram, B. C. (1992) The Ostrich Communal Nesting System. Princeton: Princeton University Press.
Brown, J. L. (1987) Helping and Communal Breeding in Birds: Ecology and Evolution. Princeton: Princeton University Press.
Bruning, D. F. (1974) “Social Structure and Reproductive Behavior in the Greater Rhea.” Living Bird 13:251—94.
Coddington, C. L., and A. Cockburn (1995) “The Mating System of Free-Living Emus.” Australian Journal of Zoology 43:365—72.
Codenotti, T. L., and F. Alvarez (1998) “Adoption of Unrelated Young by Greater Rheas.” Journal of Field Ornithology 69:58—65.
———(1997) “Cooperative Breeding Between Males in the Greater Rhea Rhea americana.” Ibis 139:568—71.
*Curry, P. J. (1979) “The Young Emu and Its Family Life in Captivity.” Master’s thesis, University of Melbourne.
Fernández, G. J., and J. C. Reboreda (1998) “Effects of Clutch Size and Timing of Breeding on Reproductive Success of Greater Rheas.” Auk 115:340—48.
*———(1995) “Adjacent Nesting and Egg Stealing Between Males of the Greater Rhea Rhea americana.” Journal of Avian Biology 26:321—24.
Fleay, D. (1936) “Nesting of the Emu.” Emu 35:202—10.
Folch, A. (1992) “Order Struthioniformes.” In J. del Hoyo, A. Elliott, and J. Sargatal, eds., Handbook of the Birds of the World, vol. 1: Ostrich to Ducks, pp. 76—110. Barcelona: Lynx Edici6ns.
*Gaukrodger, D. W. (1925) “The Emu at Home.” Emu 25:53—57.
*Heinroth, O. (1927) “Berichtigung zu ‘Die Begattung des Emus (Dromaeus novae-hollandiae)’ [Correction to ‘Mating Behavior of Emus’].” Ornithologische Monatsberichte 35:117—18.
*———(1924) “Die Begattung des Emus, Dromaeus novae-hollandiae [Mating Behavior of Emus].” Ornithologische Monatsberichte 32:29—30.
*Hiramatsu, H., K. Tasaka, S. Shichiri, and F. Hashizaki (1991) “A Case of Masculinization in a Female Ostrich.” Journal of Japanese Association of Zoological Gardens and Aquariums 33:81—84.
Navarro, J. L., M. B. Martella, and M. B. Cabrera (1998) “Fertility of Greater Rhea Orphan Eggs: Conservation and Management Implications.” Journal of Field Ornithology 69:117—20.
O’Brien, R. M. (1990) “Emu, Dromaius novaehollandiae.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 1, part A, pp. 47—58. Melbourne: Oxford University Press.
Raikow, R. J. (1968) “Sexual and Agonistic Behavior of the Common Rhea.” Wilson Bulletin 81:196—206.
*Sauer, E. G. F. (1972) “Aberrant Sexual Behavior in the South African Ostrich.” Auk 89:717—37.
Sauer, E. G. F., and E. M. Sauer (1966) “The Behavior and Ecology of the South African Ostrich.” Living Bird 5:45—75.
HUMBOLDT PENGUIN
IDENTIFICATION: A small penguin (approximately 2 feet tall) with a black band on its chest and patches of red skin at the base of its bill. DISTRIBUTION: Coastal Peru to central Chile. HABITAT: Marine areas; nests on islands or rocky coasts. STUDY AREAS: Emmen Zoo, the Netherlands; Washington Park Zoo, Portland, Oregon.
KING PENGUIN
IDENTIFICATION: A large (3 foot tall) penguin with orange ear patches and a yellow-orange wash on the breast. DISTRIBUTION: Sub-Antarctic seas. HABITAT: Oceans; nests on islands and beaches. STUDY AREA: Edinburgh Zoo, Scotland; subspecies A.p. patagonicus.
GENTOO PENGUIN
IDENTIFICATION: A medium-sized penguin (up to 21/2 feet) with a white patch above the eye. DISTRIBUTION: Circumpolar in Southern Hemisphere. HABITAT: Oceans; nests on islands and coasts. STUDY AREAS: South Georgia, Falkland Islands; Edinburgh Zoo, Scotland; subspecies P.p. papua.
Social Organization
Humboldt Penguins form mated pairs during the breeding season and nest in small colonies; they travel and feed at sea in social groups of 10—60 birds. King Penguins are highly gregarious, breeding in enormous colonies—some numbering 300,000 pairs—and generally form monogamous pair-bonds. Gentoo Penguins have a similar social system, although their nesting colonies are not as large.
Description
Behavioral Expression: Lifelong homosexual pair-bonds sometimes develop between male Humboldt Penguins. Like heterosexual pairs, same-sex partners remain together for many years: some male couples have stayed together for up to six years, until the death of one of the partners. Same-sex pairs (like opposite-sex pairs) spend much of their time close together, often touching. They also usually live together in a nest that they have built—either an underground burrow, a shallow bowl dug in the ground, or a rock niche lined with twigs. Unlike male pairs in other birds, though, homosexual pairs of Humboldt Penguins never acquire any eggs. Courtship and pair-bonding activities are also a prominent aspect of homosexual partnerships. This includes the ECSTATIC DISPLAY, in which a male stretches his head and neck upward, spreading his flippers wide and flapping them while emitting several long, very loud donkeylike brays. Sometimes this is performed mutually by both males standing side by side. Homosexual partners also ALLO-PREEN each other, affectionately running their bills through one another’s feathers. Occasional same-sex BOWING also occurs, in which one male points his beak down toward his partner and vibrates his head from side to side. As a prelude to copulation, one male approaches the other from behind, pressing against his body and vibrating his flippers against his partner; this distinctive display is known as the ARMS ACT. Homosexual copulation occurs when the bird in front lies down on his chest, allowing the other male to climb onto his back; genital contact may occur when the male being mounted holds his tail up or to the side and exposes his cloaca. Homosexual mountings are sometimes briefer than heterosexual ones, but often the two males take turns mounting each other. Not all same-sex courtship and sexual activity occurs between birds in homosexual pairs. Males who are paired to females also sometimes court and copulate with other heterosexually paired males (as well as with females other than their own mate).
In King Penguins, same-sex pairs also occur, in both males and females. These bonds are probably not as long-lasting as homosexual pairs in Humboldts, since same-sex partners sometimes divorce each other after being together for only one season (which also occurs commonly in heterosexual pairs in this species). Courtship activities are a part of King Penguin homosexual pair-bonds, especially between males. One such display is BOWING, in which one bird approaches the other while making courtly bows, often leading to mutual bowing. Another display is DABBLING, in which the birds face each other while rapidly clapping their bills and gently nibbling or preening one another’s feathers, sometimes accompanied by quivering of the flippers and tail. This may lead to homosexual copulation, in which one bird urges the other to lie down by pressing on its back, then mounts; this occurs among both males and females. In addition, female pairs sometimes lay an (infertile) egg, which they take turns incubating.
Homosexual courtship also occurs early in the breeding season among Gentoo Penguins. A male or a female brings an “offering” of pebbles or grass and lays it at the feet of another bird of the same sex, bowing and making slight hissing noises. The other bird, if interested, may respond with bowing or arranging the material into a nest. Females that pair with each other usually lay eggs in the nest that they tend together; because these birds do not typically mate with males, their eggs are infertile. However, female pairs can become successful foster parents in captivity, incubating and hatching fertile eggs when provided and successfully raising the resulting chicks.
A female King Penguin urging another female to lie down prior to mounting her
Frequency: In some zoo populations of Humboldt Penguins, at least 5 percent of all pairs are homosexual, and 12 percent of all copulations are between males. Among paired birds, 10 percent of mountings take place in male couples, while 15 percent of promiscuous matings (between nonmates) are homosexual. Of courtship displays performed by males to birds other than their partner, about a quarter of all arms acts are homosexual, and about 2 percent of courtship bows are same-sex. In one zoo colony consisting of five King Penguins, 2 out of 10 bonds that formed among the birds over a period of nine years were homosexual. Although same-sex matings have not yet been observed in these species in the wild, homosexual courtship has been seen in wild Gentoo Penguins: in one informal survey, 3 out of 13 courtships (23 percent) by Gentoos were same-sex.
Orientation: Some male Humboldt Penguins are exclusively homosexual, remaining with their male partners for their entire lives, or else re-pairing with another male should they lose their original partner. Other males are sequentially bisexual, pairing with a male after having lost one or more previous female mates. Still other males are simultaneously bisexual, engaging in both same-sex and opposite-sex courtship and copulation. Of these, some have a primary heterosexual bond but occasionally engage in homosexual activity with another breeding male: about 47 percent of all same-sex copulations are of this type (as opposed to occurring between bonded partners). In a few cases, the opposite occurs: a male with a primary homosexual pair-bond occasionally participates in a heterosexual copulation. Among King Penguins, birds in same-sex pairs are probably exclusively homosexual for the duration of their pair-bonds (since any eggs that are laid are infertile), and birds exhibit a “preference” for same-sex mates even when unpaired birds of the opposite sex are available. Over the course of their lives, however, most such birds are sequentially bisexual, since following the breakup of a homosexual pair they may go on to form heterosexual pair-bonds and even raise a family. Most Gentoo Penguins that participate in homosexual courtship are probably bisexual, since they court both males and females, albeit with a primary heterosexual orientation (since most go on to breed with birds of the opposite sex). Females that pair with each other are exclusively homosexual for the duration of their bond (which may last for one or both birds’ lives); some females pair with a heterosexual mate after the death of their female partner.
Nonreproductive and Alternative Heterosexualities
As noted above, promiscuous matings by heterosexually paired birds are common in Humboldt Penguins: one-third to one-half of all heterosexual copulations are between nonpair members, and courtship of birds other than one’s mate is also frequent. Promiscuous courtship and copulation occur in King and Gentoo Penguins as well. Even within pairs, sexual behavior may be nonprocreative. In Humboldts, copulation occurs both early and late in the breeding season, when the chances of fertilization are low or nonexistent, while heterosexual mounts (like homosexual ones) sometimes do not include genital contact or sperm transfer (in both Humboldts and Gentoos). Female Gentoo Penguins sometimes mount their mates (REVERSE mounting), while male Gentoos occasionally masturbate by mounting and copulating with clumps of grass. Males have also been observed trying to copulate with dead Penguins.
Several other variations on the lifetime monogamous pair-bond and nuclear family also occur. About a quarter of all Humboldt male-female pairs divorce, often when the female leaves her mate for another male. Divorce also occurs in 10—50 percent of Gentoo pairs, and in some years no pairs remain together. It is especially common in King Penguins, where only about 30 percent of birds retain the same mate from one season to the next. In addition, some King Penguins abandon their mates during the breeding season, and about 6 percent of chicks are reared by single parents (either abandoned or widowed). Humboldts occasionally form trios consisting of either one male and 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 CRÈCHES. These large nursery groups, sometimes containing thousands of chicks, form while the parents are away. Crèches 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: Nivå, 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 often segregated from each other and largely solitary: sometimes only one member of a pair—typically the female—migrates, though males that migrate often travel farther than females. During the winter, males and females also tend to occupy separate habitats, with males generally in more wooded areas. Griffon Vultures are much more social and tend to nest in colonies containing 15-20 pairs, sometimes as many as 50-100. As in Kestrels, mated pairs often last for many years.
Description
Behavioral Expression: In Kestrels and Griffon Vultures, two birds of the same sex—usually males—occasionally bond with each other and become a mated pair. Male Kestrels in a homosexual pair often soar together in the early spring, performing dramatic courtship display flights that reinforce their pair-bond (these displays are also found in heterosexual pairs). One such display is the ROCKING FLIGHT, in which the two partners fly at an immense height and rock from side to side, using flicking wingbeats. Another display is the slower WINNOWING FLIGHT, in which the wings beat with shallow, almost vibrating strokes, giving the impression that only the tips are moving or “shivering.” Both displays are accompanied by distinctive calls, such as the TSIK CALL—a series of clipped notes sounding like tsick or kit—and the LAHN CALL, a sequence of high-pitched trills transcribed as quirrr-rr quirrr-rr. The two males sometimes display together, or one male might soar while the other sits on his perch. Same-sex partners also copulate with each other, making the distinctive copulation call sounding like kee-kee-kee or kik-kik-kik; homosexual mounts last for 10-15 seconds (comparable to heterosexual matings).
Male Griffon Vultures in homosexual pairs also mate with each other repeatedly beginning in December (the onset of the mating season), and such pairs may remain together for years. The two males sometimes build a nest together each year—typically a flat assemblage of sticks on a crag, two to three feet across. Like Kestrels, pairs of Griffon Vultures perform a spectacular aerial pair-bonding display called TANDEM FLYING. The two birds spiral upward to a great height on a thermal, then glide downward in a path that will bring them extremely close to each other, “riding” for a few seconds one above the other, until they separate again. Although most tandem flights are by heterosexually paired birds, Vultures of the same sex also engage in this activity.
Frequency: Homosexual pairs probably occur only occasionally in Kestrels, although no systematic study of their frequency has been undertaken. Male pairs of Griffon Vultures have not yet been fully verified in the wild; however, tandem flights between same-sex partners (both males and females) account for about 20 percent of all display flights in the wild, and some of these probably represent homosexual pairings.
Orientation: No detailed studies of the life histories of birds of prey in homosexual pairs have yet been conducted. However, at least some male Griffon Vultures in same-sex tandem flights have female mates, suggesting a possible form of bisexuality, while at least some younger females in same-sex tandems likely have no prior heterosexual experience.
Nonreproductive and Alternative Heterosexualities
In any given year, many Kestrels do not breed: about a third of all birds in some populations are unpaired, while 6-13 percent of heterosexually mated birds do not lay eggs. Male-female pairs of Griffon Vultures, too, may abstain from procreating—some pairs go for as long as eight or nine consecutive years without reproducing. Nonlaying pairs, as well as younger Griffon Vultures that have not yet begun breeding, nevertheless still engage in sexual activity, often mating with each other near the breeding colonies. Several other types of nonprocreative copulations are also prominent in these species. Both Kestrels and Griffon Vultures sometimes mate outside of the breeding season (in the autumn and winter) and during the breeding season when there is no chance of fertilization. This includes during incubation, chick-raising, or very early in the season. Outside of the breeding season, though, Griffon females may refuse to participate in copulations, attacking their male partner when he tries to mount. Kestrel males and females very often live separately during the winter (as discussed above). In addition, heterosexual mating in both species occurs at astonishingly high rates, indicating that it is not simply procreative activity: Griffon heterosexual pairs sometimes mate every half hour, while Kestrels average a copulation once every 45 minutes, or seven to eight times per day during the breeding season. Even higher rates have been recorded for some Kestrels—up to three times per hour—and it is estimated that each Kestrel pair mates as many as 230 times during the breeding season alone. Male Kestrels also sometimes court and attempt to mate with females other than their mate; they usually do not succeed, though, owing to resistance by the female and defense by her mate. Nevertheless, 5-7 percent of all broods contain chicks fathered by a bird other than its mother’s mate, and in a few cases none of the nestlings are genetically related to their caretaking father. Nonmonogamous copulations probably also occur in Griffon Vultures.
Alternative heterosexual family arrangements are widespread in Kestrels: up to 10 percent of males in some years have two female mates (they usually each have families in separate nests), while a female sometimes forms a trio with two males. Divorce is fairly common in Kestrels: about 17 percent of females and 6 percent of males change partners between breeding seasons, and sometimes a pair splits during the breeding season as well. In Griffon Vultures the divorce rate is about 5 percent. Some Kestrel males are unable to provide their mates with enough food during incubation, resulting in desertion and loss of the entire clutch (accounting for more than half of all nesting failures). Finally, cannibalism has been documented in these species: Kestrel nestlings sometimes kill and eat their siblings, while parents of both species cannibalize their own chicks on rare occasions (usually if the chick has already died).
Other Species
Same-sex pairing and coparenting have been observed in other birds of prey in captivity. Female Barn Owls (Tyto alba) that are raised together occasionally bond with one another, ignoring any available males. They may even nest together, each laying a clutch of infertile eggs that they incubate side by side. Female coparents share parenting duties and can successfully raise foster young. Courtship, pair-bonding, nesting, and coparenting of foster chicks have also been documented in a pair of female Powerful Owls (Ninox strenua) from Australia. In addition, a pair of male Steller’s Sea Eagles (Haliaeetus pelagicus)—a species native to Siberia and East Asia—courted one another and built a nest together. They even incubated and hatched another eagle’s egg and successfully raised the chick together.
Sources
*asterisked references discuss homosexuality/transgender
Blanco, G., and F. Martinez (1996) “Sex Difference in Breeding Age of Griffon Vultures (Gyps fulvus).” Auk 113:247–48.
Bonin, B., and L. Strenna (1986) “The Biology of the Kestrel Falco tinnunculus in Auxois, France.” Alauda 54:241–62.
Brown, L., and D. Amadon (1968) “Gyps fulvus, Griffon Vulture.” In Eagles, Hawks, and Falcons of the World, pp. 325–28. New York: McGraw-Hill.
Cramp, S., and K. E. L. Simmons, eds. (1980) “Griffon Vulture (Gyps fulvus)” and “Kestrel (Falco tinnunculus ).” In Handbook of the Birds of Europe, the Middle East, and North Africa, vol. 2, pp. 73–81, 289–300. Oxford: Oxford University Press.
*Fleay, D. (1968) Nightwatchmen of Bush and Plain: Australian Owls and Owl-like Birds. Brisbane: Jacaranda Press.
*Heinroth, O., and M. Heinroth (1926) “Der Gansegeier (Gyps fulvus Habl.) [The Griffon Vulture].” In Die Vögel Mitteleuropas, vol. 2, pp. 66–69. Berlin and Lichterfeld: Bermühler.
*Jones, C. G. (1981) “Abnormal and Maladaptive Behavior in Captive Raptors.” In J. E. Cooper and A. G. Greenwood, eds., Recent Advances in the Study of Raptor Diseases (Proceedings of the International Symposium on Diseases of Birds of Prey, London, 1980), pp. 53–59. West Yorkshire: Chiron Publications.
Korpimaki, E. (1988) “Factors Promoting Polygyny in European Birds of Prey—A Hypothesis.” Oecologia 77:278–85.
Korpimäki, E., K. Lahti, C. A. May, D. T. Parkin, G. B. Powell, P. Tolonen, and J. H. Wetton (1996) “Copulatory Behavior and Paternity Determined by DNA Fingerprinting in Kestrels: Effects of Cyclic Food Abundance.” Animal Behavior 51:945–55.
Mendelssohn, H., and Y. Leshem (1983) “Observations on Reproduction and Growth of Old World Vultures.” In S.R. Wilbur and J. A. Jackson, eds., Vulture Biology and Management, pp. 214–41. Berkeley: University of California Press.
*Mouze, M., and C. Bagnolini (1995) “Le vol en tandem chez le vautour fauve (Gyps fulvus) [Tandem Flying in the Griffon Vulture].” Canadian Journal of Zoology 73:2144–53.
*Olsen, K. M. (1985) “Pair of Apparently Adult Male Kestrels.” British Birds 78:452–53.
Packham, C. (1985) “Bigamy by the Kestrel.” British Birds 78:194.
*Pringle, A. (1987) “Birds of Prey at Tierpark Berlin, DDR.” Avicultural Magazine 93:102–6.
Sarrazin, F., C. Bagnolini, J. L. Pinna, and E. Danchin (1996) “Breeding Biology During Establishment of a Reintroduced Griffon Vulture Gyps fulvus Population.” Ibis 138:315–25.
Stanback, M. T., and W. D. Koenig (1992) “Cannibalism in Birds.” In M. A. Elgar and B. J. Crespi, eds., Cannibalism: Ecology and Evolution Among Diverse Taxa, pp. 277–98. Oxford: Oxford University Press.
Terrasse, J. F., M. Terrasse, and Y. Boudoint (1960) “Observations sur la reproduction du vautour fauve, du percnoptère, et du gypaete barbu dans les Basses-Pyrénées [Observations on the Reproduction of the Griffon Vulture, the Egyptian Vulture, and the Bearded Vulture in the Lower Pyrenees].” Alauda 28:241–57.
Village, A. (1990) The Kestrel. London: T. and A. D. Poyser.
SAGE GROUSE
IDENTIFICATION: A gray-brown grouse with speckled plumage, pointed tail feathers, and inflatable air sacs in the breast. DISTRIBUTION: Western North America. HABITAT: Sage grassland, semidesert. STUDY AREAS: Green River Basin and Laramie Plains, Wyoming; Long Valley, California.
RUFFED GROUSE
IDENTIFICATION: A large grouse with a banded, fan-shaped tail and distinctive black ruffs on the side of the neck. DISTRIBUTION: Northern and central North America. HABITAT: Forest. STUDY AREA: In captivity in Ithaca, New York.
Social Organization
During the breeding season, male Ruffed and Sage Grouse display on territories—large, communal “strutting grounds” or LEKS in Sage Grouse, and individual “drumming logs” in Ruffed Grouse. Both species have a promiscuous mating system, in which birds mate with multiple partners, do not form pair-bonds, and females care for the young with no male assistance. Outside of the mating season, birds sometimes congregate in mixed-sex flocks.
Description
Behavioral Expression: At dawn on their prairie display grounds, female Sage Grouse gather in groups of eight to ten (or sometimes more) known as CLUSTERS. Although many are there to mate with males, some females also court and mate with each other. Homosexual courtship display is similar to that used by males and is called STRUTTING. The female takes short steps forward and turns while presenting herself in a spectacular posture—long tail feathers fanned in a circle, air sacs in the breast expanded, and neck feathers erected and rustling. Unlike males, however, strutting females do not make the characteristic “plopping” sound during courtship, owing to the smaller size of their air sacs. When the female has finished her strut, another female may solicit a copulation from her by crouching down, arching her wings and fanning the wing feathers on the ground. The other female mounts her and often performs a complete mating sequence, spreading her wings on either side of the mounted female for balance, treading on her back with her feet, and lowering and rotating the tail for cloacal (genital) contact. Some females also chase others in the group and try to mount them, and “pile-ups” of three or four females all mounted on each other sometimes develop. During most lesbian matings, males pay no attention to the females. Sometimes, however, they try to disrupt a lesbian mounting, or they may even try to join in by mounting a female who is herself mounted on another female. In one case, a male even mounted another male who was himself mounted on two females that were mounting each other! Later in the breeding season, two females also sometimes jointly parent their offspring, combining all their chicks into a single brood that they both look after.
Homosexual courtship in Sage Grouse: a female performing the “strutting” display on the plains of Wyoming
Male Ruffed Grouse also court and mount each other. Deep in the forest, each male advertises his presence by DRUMMING at dawn or dusk, producing a throbbing, drumroll-like sound by rapidly “beating” the air with his wings. If another Grouse lands on the drumming log, he begins his strutting display. Fanning his tail like a turkey, he lowers his wings, erects his neck ruffs, and rotates his head vigorously, all the while emitting a hissing sound as he approaches the other bird. If the other bird is a female, mating takes place, whereas if it is another male, typically a fight will ensue. However, in some cases the other male does not challenge the displaying male. The courting male then makes a “gentle” approach, sleeking down his feathers, dragging his tail on the ground, and occasionally shaking his head. He sometimes pecks softly at the base of the other male’s bill or places his foot on the other’s back and may mount him as in heterosexual copulation (although the mounted bird does not usually adopt the female’s typical copulatory posture).