Biological Exuberance: Animal Homosexuality and Natural Diversity

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.