Study: same-sex and mixed bird couples equally faithful

A recent study published by a UC Berkeley postdoctoral scholar shows that same-sex pairs of one type of monogamous bird have relationships that are just as faithful and strong as those of male-female pairs.

Julie Elie, currently a campus postdoctoral scholar, began her research on zebra finches in 2007 at the University of Saint Etienne, looking to examine how different types of relationships influence communication between the birds.

In the study — published online Aug. 6 in the journal Behavioral Ecology and Sociobiology — Elie and her two colleagues found that male zebra finch pairs exhibited different types of communication as well as behaviors displayed in heterosexual pairs.

“Male–male and female–female same-sex bonds display the same behavioral characteristics as male–female ones: they are intense, highly selective, and stable affinitive relationships involving the same behavioral displays already described in wild birds,” the study reads. “Because the pair-bond in socially monogamous species represents a partnership that may give advantages for survival … we propose that same sex pairing in the zebra finch may result from the pressure to find a social partner.”

In her research, Elie used five groups of adult zebra finches: two same-sex groups of only males or females and three mixed groups of varied sex ratio.

“Either they could choose to interact with all the birds or what we observed — still they did interact with only one particular individual,” Elie said. “That was a sign they had well-established, clear pair-bonds.”

In the male-only groups of zebra finches — a type of bird that typically forms long-lasting monogamous relationships with members of the opposite sex — Elie observed that they exhibited similar behaviors as those birds in heterosexual pairs, such as private duets of calls, preening each other and touching their beaks together.

According to Elie, even the introduction of new potential mates did not split the majority of the couples. When females were introduced into the cage of eight male-male pairs, five of the couples remained together.

“This indicates something else,” Elie said. “It’s not just a sexual relationship. There are also social things going on.”

Previously, all research has been focused on the reproductive behaviors of same-sex animals, Elie said. However, the research she conducted along with Clementine Vignal and Nicolas Mathevon from the University of Saint Etienne more closely examined the social aspects of such relationships.

“This is quite new to describe a same-sex relationship using the whole behaviors those birds were expressing,” she said.

Though Elie said she plans to continue different research involving communication between birds with a more sensory point of view — how birds perceive different types of calls — she said that her research has raised some important questions for future research on this topic, specifically in examining female-female relationships.

Allie Bidwell is the news editor.