An estimated one-quarter of all black swans pairings are of homosexual males. They steal nests, or form temporary threesomes with females to obtain eggs, driving away the female after she lays the eggs. More of their cygnets survive to adulthood than those of different-sex pairs, possibly due to their superior ability to defend large portions of land. The same reasoning has been applied to male flamingo pairs raising chicks.
Studies have shown that 10 to 15 percent of female western gulls in some populations in the wild exhibit homosexual behavior.
Mallards form male-female pairs only until the female lays eggs, at which time the male leaves the female. Mallards have rates of male-male sexual activity that are unusually high for birds, in some cases, as high as 19% of all pairs in a population.
In early February 2004 the New York Times reported that Roy and Silo, a male pair of chinstrap penguins in the Central Park Zoo in New York City had successfully hatched and fostered a female chick from a fertile egg they had been given to incubate. Other penguins in New York zoos have also been reported to have formed same-sex pairs.
Zoos in Japan and Germany have also documented homosexual male penguin couples.The couples have been shown to build nests together and use a stone as a substitute for an egg. Researchers at Rikkyo University in Tokyo found 20 homosexual pairs at 16 major aquariums and zoos in Japan.
Bremerhaven Zoo in Germany attempted to encourage reproduction of endangered Humbolt penguins by importing females from Sweden and separating three male pairs, but this was unsuccessful. The zoo's director said that the relationships were "too strong" between the homosexual pairs. German gay groups protested at this attempt to break up the male-male pairs but the zoo's director was reported as saying "We don't know whether the three male pairs are really homosexual or whether they have just bonded because of a shortage of females... nobody here wants to forcibly separate homosexual couples."
A pair of male Magellanic penguins who had shared a burrow for six years at the San Francisco Zoo and raised a surrogate chick, split when the male of a pair in the next burrow died and the female sought a new mate.
Buddy and Pedro, a pair of male African Penguins, were separated by the Toronto Zoo to mate with female penguins.Buddy has since paired off with a female.
In 1998 two male Griffon vultures named Dashik and Yehuda, at the Jerusalem Biblical Zoo, engaged in "open and energetic sex" and built a nest. The keepers provided the couple with an artificial egg, which the two parents took turns incubating; and 45 days later, the zoo replaced the egg with a baby vulture. The two male vultures raised the chick together.A few years later, however, Yehuda became interested in a female vulture that was brought into the aviary. Dashik became depressed, and was eventually moved to the zoological research garden at Tel Aviv University where he too set up a nest with a female vulture.
Two homosexual male vultures at the Allwetter Zoo in Muenster built a nest together, although they were picked on and often had their nest materials stolen by other vultures. They were eventually separated to try to promote breeding by placing one of them with female vultures, despite the protests of German homosexual groups.
Both male and female pigeons sometimes exhibit homosexual behavior. As well as sexual behavior same-sex pigeon pairs will build nests, and hens will lay (infertile) eggs and attempt to incubate them.
The Amazon River dolphin or boto has been reported to form up in bands of 3–5 individuals enjoying group sex. The groups usually comprise young males and sometimes one or two females. Sex is often performed in non-reproductive ways, using snout, flippers and genital rubbing, without regards to gender.In captivity, they have been observed to sometimes perform homosexual and heterosexual penetration of the blowhole, a hole homologous with the nostril of other mammals, making this the only known example of nasal sex in the animal kingdom. The males will sometimes also perform sex with tucuxi males, a small porpoise.
