Biological Exuberance: Animal Homosexuality and Natural Diversity

Swallow-tailed Manakin (Foster 1987:555); Laughing Gull (Noble and Wurm 1943:205); Black-headed Gull (van Rhijn and Groothuis 1985:163). Conversely, homosexuality has sometimes been attributed to behavioral identity between males and females. In Ruffed Grouse, for example, the nonaggressive or “submissive” posture of a male is similar to the behavior of a female during courtship, and that males court both sexes is attributed to their inability to distinguish “female-acting” males from actual females (Allen 1934:185; see also the discussion of “pseudoheterosexuality” earlier in this chapter). Aside from the fact that males and females are very different visually from each other in this species and therefore “there is no excuse for a male not recognizing a female” (as Allen [1934:180-81] observes), in the related red grouse there is a parallel identity between male “submissive” and female courtship behavior, yet males do not court other males in this species (Watson, A., and D. Jenkins [1964] “Notes on the Behavior of the Red Grouse,” British Birds 57:157).

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Tree Swallow (Stutchbury and Robertson 1987a:719-20, 1987b:418). It is also unlikely that homosexual activity between adult males results from their mistaking one another for (adult) females. As Lombardo et al. (1994) point out, although the two sexes in this species look similar, the sex of at least one male involved in homosexual activity was nevertheless identifiable from his cloacal (genital) protuberance, lack of brood patch, and wing length. Most adult females are also visually distinct from males owing to the presence of a brown patch on the forehead (shorter wings also distinguish subadult females from subadult males) (Stutchbury and Robertson 1987c). In addition, same-sex copulations appear to be fairly uncommon in this species (Lombardo, personal communication)—certainly they are not nearly as frequent as one would expect if “mistakes” in sex recognition were prevalent.

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Black-headed Gull (van Rhijn 1985:87, 100).

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Hooded Warbler (Niven 1993:191) (cf. Lynch et al. [1985:718] for mean dimensions of other males). Niven (1993 and personal communication) suggests that it was also the female behavior patterns of this male that “triggered” the homosexual pairing, yet this bird’s behavior was actually a mixture of male and female patterns, involving, for example, incubation (female duties) as well as singing (male). Moreover, male Hooded Warblers are particularly attuned to differences in song pattern, using this information to recognize individual birds and then storing it in long-term memory for future use (Godard 1991). Because this male’s singing was highly distinctive, it is improbable that other males simply “disregarded” this aspect of his behavior or were “unaware” of his male status (especially given his physical characteristics). Furthermore, all “female” behaviors recorded in this individual occurred after the formation of the pair-bond—since pairs were not observed early in the breeding season, we do not in fact know whether this individual exhibited any (or only) “femalelike” patterns during courtship and pair-formation.

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Hooded Warbler: differential attacking of males (Stutchbury 1994:65-67); mating success of malelike females (as evidenced by the fact that nests are fairly equally distributed between dark and light females) (Stutchbury et al. 1994:389[fig.6]; Stutchbury and Howlett 1995:95); promiscuous mating attempts on hooded females (Stutchbury et al. 1994:388).

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