Humans make a big hoo-ha about issues surrounding same sex marriage, but in the bird world, homosexual bonds are often as natural — and as long-lasting — as heterosexual pairings.

At least, that's the finding of a new study of zebra finches that discovered that same sex pairs of monogamous birds were just as faithful and dedicated as their heterosexual brethren, even after the birds were introduced to members of the opposite sex.

The study, reported by the BBC and published in the journal Behavioural Ecology and Sociobiology, suggests that mating amounts to much more than just reproduction. It also indicates that homosexual bonds may play an important, though little-understood, biological role in the organization of some bird colonies.

"Relationships in animals can be more complicated than just a male and a female who meet and reproduce, even in birds," said lead researcher Julie Elie. "A pair bond in socially monogamous species represents a cooperative partnership that may give advantages for survival. Finding a social partner, whatever its sex, could be a priority."

Zebra finches are known to establish lifelong monogamous relationships that are routinely consummated through behavior such as birdsong, mutual preening and beak nuzzling. Although same-sex pairings are not uncommon between zebra finches, researchers were unsure of just how strong the bonds were.

Through the first stage of the study, young finches were raised in same-sex groups. After more than half of the birds bonded with same-sex mates, researchers then monitored their behavior to see how the bonds compared to typical heterosexual pairings. Sure enough, the same sex pairs groomed their partners, nuzzled beaks, sang to one another, and even built nests as a team just as opposite sex pairs would.

The second stage of the study saw novel females introduced to the group of bonded male-male pairs. Five out of the eight males in the study showed no interest in the females at all, and simply continued their relationship with their male partner indefinitely. This fidelity proved to researchers that the bond itself was more important to the birds than the need to reproduce.

Though this study was limited to a single group of zebra finches, strong homosexual bonds have been observed throughout the avian world. For instance, at least two cases of homosexual bonds have been observed among captive penguins. One of these pairs built a nest together, and they even adopted an egg (donated by the zoo's keepers), incubated it and hatched a chick together.

In the wild, homosexual pairings between monogamous gulls and albatrosses are also common, even when the birds have options as to which sex to mate with. In fact, female-female pairs have been observed copulating with a male, but raising the resultant chick together.

Bryan Nelson ( @@brynelson ) writes about everything from environmental problems here on Earth to big questions in space.

Homosexual bird marriages just as strong as heterosexual ones
Study shows that mating is about much more than just the need to reproduce.