Study counts the high cost of infidelity for swift parrots

Scientists at ANU have found a chronic shortage of females in a critically endangered parrot species has led to love triangles, sneaky sex on the side, increased fighting between males and fewer babies. The ratio of males to females among swift parrots was once roughly equal but it has increased over time to almost three to one, since the introduction of a tiny predator to Tasmania in the 1800s - the sugar glider. Sugar gliders can access nest hollows and kill female swift parrots while they incubate their eggs. More than half of the females die each year at their breeding grounds in Tasmania. Lead researcher Professor Rob Heinsohn said the research team studied the swift parrot mating system using molecular techniques and found more than half of the nests had babies with more than one father. "This is remarkable for parrots because most species are monogamous," said Professor Heinsohn from the ANU Fenner School of Environment and Society. The study, which is published in the  Journal of Animal Ecology , found mate sharing was not beneficial for anyone in the ménage à  trois .