And finally, in many species (e.g., Greylag Geese, Oystercatchers), individuals form bisexual trios that parent offspring together (often contrasting with heterosexual trios and/or homosexual pairs within the same species).⁶⁷
67. Western Gull (Hunt et al. 1984); Black-winged Stilt (Kitagawa 1988); Lesser Scaup Duck (Afton 1993; Munro 1941); Acorn Woodpecker (W. D. Koenig, personal communication); Squirrel Monkey (Ploog 1967:159-60); Greylag Goose (Lorenz 1979, 1991); Oystercatcher (Heg and van Treuren 1998). Although female coparents in Acorn Woodpeckers are "platonic" in that they do not specifically engage in courtship or sexual behavior with one another, they still participate in group mounting displays characteristic of this species (which usually include homosexual mounting and may actually involve mounting of their coparent).
"Biological Exuberance: Animal Homosexuality and Natural Diversity" - Bruce Bagemihl
I am still sorting through the thousands of bird pictures that I've took in Portugal (yes, so many, 4318 to be precise). But I also tried to take some videos for the first time. As you can see, it is a bit shaky, because I've only mounted my heavy camera/lens on a monopod. Also, the video seems to be a bit fast, so I guess I have to look at the settings. Nevertheless, I think it is quite enjoyable to watch this black-winged stilt search for food in the shallow water. They were everywhere, well in every mudflat, and I quite like watching them stalking around on those long red legs.
Both females take turns incubating the eggs; in heterosexual pairs the two birds also share incubation duties, but in many cases the female contributes a disproportionately greater amount of time than does the male.
A nest with a "supernormal clutch" of eggs belonging to a pair of female Black-winged Stilts in Japan
"Biological Exuberance: Animal Homosexuality and Natural Diversity" - Bruce Bagemihl
Because the eggs they lay are usually infertile, it is likely that many female Black-winged Stilts in lesbian pairs are exclusively homosexual, i.e., they do not copulate with males (at least for the duration of their bond).
"Biological Exuberance: Animal Homosexuality and Natural Diversity" - Bruce Bagemihl