Only it's the boys doing it. And they're guppies:
Some female animals are known to show a preference for mating with males they had observed coupling with other females in a phenomenon known as "mate choice copying." This allows them to evaluate the quality of a potential mate from a distance. For this study, the researchers set out to show that homosexual behaviour in the tropical freshwater fish Poecilia mexicana would similarly boost a drabber male's chances of heterosexual coupling.
"P. mexicana females increase their preference for initially non-preferred males not only after observing those males interacting sexually with females, but also when having observed them initiating homosexual behaviour.... As homosexual behaviour is regularly seen in small P.mexicana males, we speculate that it might represent an alternative mating tactic used by subordinate, and thus, less attractive males," the University of Frankfurt researchers wrote.