Foundation.
Garnett, S. T. (1980) “The Social Organization of the Dusky Moorhen, Gallinula tenebrosa Gould (Aves: Rallidae).” Australian Wildlife Research 7:103- 12.
*———(1978) “The Behavior Patterns of the Dusky Moorhen, Gallinula tenebrosa Gould (Aves: Rallidae).” Australian Wildlife Research 5:363-84.
Gibbs, H. L., A. W. Goldizen, C. Bullough, and A. R. Goldizen (1994) “Parentage Analysis of Multi-Male Social Groups of Tasmanian Native Hens (Tribonyx mortierii): Genetic Evidence for Monogamy and Polyandry.” Behavioral Ecology and Sociobiology 35:363— 71.
Goldizen, A. W., A. R. Goldizen, and T. Devlin (1993) “Unstable Social Structure Associated with a Population Crash in the Tasmanian Native Hen, Tribonyx mortierii.” Animal Behavior 46:1013- 16.
Goldizen, A. W., A. R. Goldizen, D. A. Putland, D. M. Lambert, C. D. Millar, and J. C. Buchan (1998) “‘Wife- sharing’ in the Tasmanian Native Hen (Gallinula mortierii): Is It Caused By a Male-biased Sex Ratio?” Auk 115:528—32.
*Jamieson, I. G., and J. L. Craig (1987a) “Male-Male and Female-Female Courtship and Copulation Behavior in a Communally Breeding Bird.” Animal Behavior 35:1251-53.
———(1987b) “Dominance and Mating in a Communal Polygynandrous Bird: Cooperation or Indifference Towards Mating Competitors?” Ethology 75:317-27.
Jamieson, I. G., J. S. Quinn, P. A. Rose, and B. N. White (1994) “Shared Paternity Among Non-Relatives Is a Result of an Egalitarian Mating System in a Communally Breeding Bird, the Pukeko.” Proceedings of the Royal Society of London, Series B 257:271-77.
*Lambert, D. M., C. D. Millar, K. Jack, S. Anderson, and J. L. Craig (1994) “Single- and Multilocus DNA Fingerprinting of Communally Breeding Pukeko: Do Copulations or Dominance Ensure Reproductive Success?” Proceedings of the National Academy of Sciences 91:9641—45.
*Ridpath, M. G. (1993) “Tasmanian Native-hen, Tribonyx mortierii.” In S. Marchant and P. J. Higgins, eds., Handbook of Australian, New Zealand, and Antarctic Birds, vol. 2, pp. 615—24. Melbourne: Oxford University Press.
*———(1972) “The Tasmanian Native Hen, Tribonyx mortierii. I. Patterns of Behavior. II. The Individual, the Group, and the Population.” CSIRO Wildlife Research 17:1—90.
*Swengel, S. R., G. W. Archibald, D. H. Ellis, and D. G. Smith (1996) “Behavior Management.” In D. H. Ellis, G. F. Gee, and C. M. Mirande, eds., Cranes: Their Biology, Husbandry, and Conservation, pp. 105—22. Washington, D.C.: National Biological Service; Baraboo, Wis.: International Crane Foundation.
IDENTIFICATION: A medium-sized brown, storklike bird with a prominent crest almost as long as its bill. DISTRIBUTION: Throughout tropical Africa from Senegal to east and south Africa; Madagascar. HABITAT: Wetlands, including savanna and woodland near water. STUDY AREAS: Near Niono, Mali; Karen and Nairobi, Kenya.
Social Organization
Hammerheads are usually found in pairs or groups of 8—10 individuals, though larger groups of up to 50 birds may also congregate. The mating system is believed to involve monogamous pair-bonds. Couples build extraordinarily large domed nests, often several on the same territory.
Description
Behavioral Expression: Hammerheads engage in a striking group courtship ceremony that includes same-sex mounting. Gathering at dawn on open lawns, riverbanks, rocks, or in the trees, groups of 3—20 birds (including some mated pairs) begin calling in unison. Their calls consist of a series of loud, high-toned yips that develop into a rapid sequence of “purring” or trilling notes, often accompanied by wing-flapping. Two or more birds may then perform a NODDING DISPLAY to each other, in which the bill is rapidly bobbed up and down (sometimes still accompanied by the YIP-PURR chorus), or pairs of birds may run in circles side by side. The culmination of this spectacular display is a series of mountings, initiated when one bird runs up to another, drooping and flicking its wings while it raises and lowers its crest, or when one bird solicits another by crouching, cocking its tail, and partially opening its wings. One Hammerhead then hops onto the back of the other, similar to a heterosexual copulation—except that, in addition to males mounting females, males also mount other males, and females mount females as well as males. The mounting bird beats its wings and gives the YIP-PURR call, while the mounted bird presses its tail up against the lowered tail of the mounter (though no cloacal [genital] contact takes place). Sometimes the two birds face in opposite directions; reciprocal mounting (mounter and mountee exchanging positions, often several times in succession) also occurs, as do “pile-ups” of three or four birds all mounted on each other.
A female Hammerhead mounting another female
Frequency: Social courtship displays including ritualized same- sex mounting occur commonly in Hammerheads throughout the year. Each mounting session lasts for 10—40 minutes and may include dozens of mountings.
Orientation: All Hammerheads participate in group courtship displays, and most birds are probably involved in both same-sex and opposite-sex mountings.
Nonreproductive and Alternative Heterosexualities
As noted above, nonprocreative heterosexual activity (REVERSE mounting, as well as male-female mounts without cloacal contact) is common in Hammerheads. In addition, a significant percentage of heterosexual pairs may be nonbreeders. In some populations, as many as three-quarters of nests go unused (although some of these are “extra” nests built by breeding pairs), and couples may forgo breeding for four or more years at a time.
Other Species
Same-sex pairing occurs in semiwild White Storks (Ciconia ciconia) in some European populations, and individuals form homosexual pairs even when numerous opposite-sex partners are available. Same-sex pairs are able to successfully incubate, hatch, and raise foster young.
Sources
*asterisked references discuss homosexuality/transgender
*Brown, L. H. (1982) “Scopidae, Hamerkop.” In L. H. Brown, E. K. Urban, and K. Newman, eds., The Birds of Africa, vol. 1, pp. 168—72. London and New York: Academic Press.
*Campbell, K. (1983) “Hammerkops.” E.A.N.H.S. (East Africa Natural History Society) Bulletin (January-April): 11. 1.
Cheke, A. S. (1968) “Copulation in the Hammerkop Scopus umbretta.” Ibis 110:201—3.
*Elliott, A. (1992) “Scopidae (Hamerkop).” In J. del Hoyo, A. Elliott, and J. Sargatal, eds., Handbook of the Birds of the World, vol. 1, Ostrich to Ducks, pp. 430—35. Barcelona: Lynx Edicions.
Goodfellow, C. F. (1958) “Display in the Hamerkop, Scopus umbretta.” Ostrich 29:1—4.
Kahl, M. P. (1967) “Observations on the Behavior of the Hamerkop Scopus
