Sex And The Single Gull: Females Pair Up To Help Chicks
Life is impossible if you’re a single sea gull trying to raise chicks in a world full of predators and aggressive neighbors.
“These gulls have to go out daily to feed, and if you leave your eggs or chicks undefended for even a few minutes, when you come back they won’t be there,” says Michael Conover, a professor of wildlife science at Utah State University. “If you are a gull, there is no such thing as a single-parent family.”
And that, says Conover, is why some females form homosexual pairs with other females in several species of terns and gulls. Female-female pairs are found in up to 2 percent of California gulls - Utah’s state bird - and up to 5 percent of ring-billed gulls, which also are common in Utah.
During two decades of research, Conover found female gulls form same-sex pairs when too few males are present, possibly due to pollution.
“There is some female-female pairing in almost every gull colony in Utah,” Conover says. “It’s a natural phenomenon in gulls. Female-female pairing seems to occur because of a shortage of males. It is an adaptive strategy gulls adopt when they can’t find a male mate.”
Gulls in female-female pairs sometimes mount each other, but their alliance “is not a sexual behavior,” Conover says. Each female in the pair will copulate with a male that already has a female mate. Then the homosexual females share a nest and lay their eggs in it.
“The two females will share incubation and chick-rearing responsibilities,” says Conover. “One will baby-sit while the other is out feeding.”
Conover’s research was highlighted recently in a Science News magazine article about animal homosexuality. Conover started studying sea gulls at Washington State University, where he earned master’s degrees in zoology and psychology and a doctorate in zoology.