University of California, Berkeley neuroscience and psychology researcher Julie Elie uncovered the behavior while studying zebra finches.
After raising young male finches in the absence of females, more than half of the males paired, eventually singing and preening each other as if they were a breeding pair.
Once females finches were introduced into the mix, five of the eight males involved in same-sex pair bonds ignored the females and retained the bond with their male partner.
Elie wrote in the journal Behavioral Ecology and Sociobiology that “relationships in animals can be more complicated than just a male and a female who meet and reproduce, even in birds.”
There have been several other examples of same-sex bonding observed in the avian world, including female gull and albatross couples that raise their young after brief mating encounters with males.
Photos: Julie Elie - UC Berkley