Aussie scientist publishes theory of bird homosexuality

A University of Newcastle biologist has published a theory explaining the frequency of homosexual behaviour in different bird species.

In earlier research Dr Geoff MacFarlane found that male-to-male sexual pairings were more common in bird species where males played less of a role raising offspring and mated with multiple partners, while female-to-female pairings were more common in species that paired monogamously and shared parental responsibilities.

In a new paper published in the journal Animal Behaviour, MacFarlane argues that homosexual behaviour is not necessarily a disadvantage to birds in reproducing.

“In evolutionary literature, homosexual behaviour has always been seen as a cost to reproductive success based on the assumption that if you’re engaging in homosexual behaviour it’s going to reduce your chances of reproducing,” MacFarlane told Southern Star Observer.

“We’re arguing that that’s not always the case. Birds in species where their parental care load is lower are going to spend more time looking for other reproductive opportunities.

“So where there are lots of reproductive opportunities, homosexual behaviour can occur as well without really influencing reproductive success. Rather than it being an impact on reproduction it can exist quite happily along with it.”

MacFarlane, an ecotoxicologist, told SSO what drew him to study homosexuality in animals.

“Although ecotoxicology is my primary field I also have an interest in animal behaviour,” he said. “In 1999 a book was published called Biological Exuberance [by Bruce Bagemihl] about homosexual behaviour in animals.

“I read that and thought, ‘Wow, this is happening everywhere’.  Not much work had been done to try to understand the patterns of its occurrence so that led me to start thinking about that from an evolutionary slant.”

MacFarlane said there was a lot of variation between species in frequency of homosexual behaviour.