Bruce Bagemihl - Biological Exuberance

*asterisked references discuss homosexuality/transgender

*Fjeldså, J. (1983) “Social Behavior and Displays of the Hoary-headed Grebe Poliocephalus poliocephalus.” Emu 83:129–40.

Fjeldså, J. and N. Krabbe (1990) Birds of the High Andes. Copenhagen: Zoological Museum, University of Copenhagen; Svendborg, Denmark: Apollo Books.

Johnsgard, P. A. (1987) Diving Birds of North America. Lincoln and London: University of Nebraska Press.

*Nuechterlein, G. L., and R. W. Storer (1989) “Reverse Mounting in Grebes.” Condor 91:341—46.

*O‘Brien, R. M. (1990) “Hoary-headed Grebe, Poliocephalus poliocephalus.’ In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 1, pp. 100—107. Melbourne: Oxford University Press.

Storer, R. W. (1969) “The Behavior of the Horned Grebe in Spring.” Condor 71:180—205.

IDENTIFICATION: A stocky, medium-sized (2 foot long) heron with a black crown and back, white underparts, gray wings, and white ribbon plumes at the nape of the neck. DISTRIBUTION: Over much of Europe, Asia, Africa, and North and South America. HABITAT: Wetlands. STUDY AREAS: American Museum of Natural History, New York; Altenberg, Austria; subspecies N.n. hoactli and N.n. nycticorax.

Black-crowned Night Herons are fairly gregarious birds, gathering in colonies that may contain hundreds or thousands of individuals nesting close together. Monogamous pairs predominate during the mating season.

Behavioral Expression: Male Black-crowned Night Herons sometimes court other males and form homosexual pairs. To attract other birds, a male performs the SNAP-HISS CEREMONY, in which he repeatedly extends and lowers his head with erected plumes while “treading” with his feet and making a combined snapping (or clicking) and hissing sound. This courtship display is directed at both males and females. While most males are not interested in the ceremony, those that are attracted go on to participate in an OVERTURE display (also used in heterosexual courtship). In this activity, one or both males stretch their heads forward (again with feathers raised) while making their eyeballs protrude from their sockets, at the same time clicking and touching their bills. Males in homosexual pairs also mount each other (in the position used for heterosexual copulation); both males may mount or be mounted, although individuals sometimes show a preference for one or the other activity. Typically one male in the pair also builds a nest out of twigs; sometimes this occurs before the pair-bond forms, or else the two males may search for a nest site together. Once the pair-bond is established, both males vigorously defend their territory against other birds. Homosexual pair-bonds are strong, lasting the entire breeding season (as do heterosexual bonds). Young Black-crowned Night Herons also form pairs or “companionships,” some of which are between birds of the same sex (although no overt sexual behavior occurs between companions of either the same or opposite sex). Occasionally, a juvenile female may even bond with more than one other female. Although no homosexual pairs between adult females have yet been observed, females sometimes perform typically male courtship displays such as the snap-hiss ceremony.

Frequency: In some captive populations, homosexual pairs in adult males make up more than 20 percent of all pairings, while 38 percent of juvenile pairs are same-sex (three-quarters of which are between females). The incidence of same-sex pairs in the wild is not known. Adult male partners may mount each other more than 30 times over the mating season.

Orientation: During the courtship phase, males exhibit a form of simultaneous bisexuality by displaying to both sexes, and some males are clearly more attracted to same-sex courtships than others. Most young females that form same-sex bonds only pair with other females, while a few form both homosexual and heterosexual pair-bonds. Once a homosexual bond has formed, though, the birds will maintain the bond even if they are separated for several weeks, returning to their same-sex partner when reunited rather than establishing a heterosexual bond. Some birds may exhibit sequential bisexuality, forming heterosexual bonds after participating in homosexual pairings when young (or vice versa).

Male-female relations in Black-crowned Night Herons are sometimes fraught with complications. Heterosexual copulation is often incomplete because females refuse to cooperate in mating. In addition, in the early stages of courtship, males are often aggressive toward any bird that approaches them, including females. Chicks that hatch late are usually deserted by their parents after their siblings have fledged; they often move to other nests and are adopted by those families. Adults also occasionally accept eggs laid in their nest by other herons such as great egrets ( Casmerodius albus ) or lay their own eggs in nests of other species such as snowy egrets ( Egretta thula ).

*asterisked references discuss homosexuality/transgender

Allen, R. P., and F. P. Mangels (1940) “Studies of the Nesting Behavior of the Black-crowned Night Heron.” Proceedings of the Linnaean Society of New York 50–51:1–28.

Cannell, P. E, and B. A. Harrington (1984) “Interspecific Egg Dumping by a Great Egret and Black-crowned Night Herons.” Auk 101:889-91.

Davis, W. E., Jr. (1993) “Black-crowned Night Heron ( Nycticorax nycticorax ) .” In A. Poole and F. Gill, eds., The Birds of North America: Life Histories for the 21 st Century, no. 74. Philadelphia: Academy of Natural Sciences; Washington, D.C.: American Ornithologists’ Union.

Gross, A. O. (1923) “The Black-crowned Night Heron ( Nycticorax nycticorax naevius ) of Sandy Neck.” Auk 40:1–30, 191–214.

Kazantzidis, S., V. Goutner, M. Pyrovetsi, and A. Sinis (1997) “Comparative Nest Site Selection and Breeding Success in 2 Sympatric Ardeids, Black-Crowned Night-Heron ( Nycticorax nycticorax ) and Little Egret ( Egretta garzetta ) in the Axios Delta, Macedonia, Greece.” Colonial Waterbirds 20:505–17.

*Lorenz, K. (1938) “A Contribution to the Comparative Sociology of Colonial-Nesting Birds.” In F. C. R. Jourdain, ed., Proceedings of the Eighth International Ornithological Congress, Oxford (July 1934), pp. 207–21. Oxford: Oxford University Press.

McClure, H. E., M. Yoshii, Y. Okada, and W. F. Scherer (1959) “A Method for Determining Age of Nestling Herons in Japan.” Condor 61:30–37.

*Noble, G. K., and M. Wurm (1942) “Further Analysis of the Social Behavior of the Black-crowned Night Heron.” Auk 59:205–24.

*Noble, G. K., M. Wurm, and A. Schmidt (1938) “Social Behavior of the Black-crowned Night Heron.” Auk 55:7–40.

Schorger, A. W. S. (1962) “Black-crowned Night Heron.” In R. S. Palmer, ed., Handbook of North American Birds, vol. 1: Loons through Flamingos, pp. 472–84. New Haven and London: Yale University Press.

IDENTIFICATION: Long-legged, typically white herons with ornamental, filamentous plumes on the back, breast, and nape; these are golden-buff-colored in the Cattle Egret. DISTRIBUTION: Throughout Africa, southern Europe, Australasia, and (in Cattle Egret) North and South America. HABITAT: Variable, including swamps, marshes, rivers, lakes, meadows. STUDY AREA: Near Tsu City, Japan; subspecies Bj. coromanda and E.g. garzetta.