Shortage of female swift parrots caused by sugar gliders wreaking ‘havoc’ on mating
Calla Wahlquist
Tue 4 Dec 2018 17.00 GMTLast modified on Wed 5 Dec 2018 14.16 GMT
Tasmania’s critically endangered swift parrots are facing a new threat to survival – polyamory.
A study by researchers at the Australian National University, published in the Journal of Animal Ecology, has found that a chronic shortage of female swift parrots caused by intensive predation by sugar gliders has wreaked havoc on the bird’s usually monogamous breeding habits and lowered the survival rate for young hatchlings.
Lead researcher Prof Rob Heinsohn said the unusual behaviour was caused by a significant disparity in the number of males and females in the parrots’ breeding grounds of the blue gum forests in south-east Tasmania. Surplus bachelor males were pressuring paired-up females for sex and getting into fights with paired males.
Heinsohn said that predation by sugar gliders, which were introduced to Tasmania from mainland Australia in the 1800s, had changed the gender ratio in the swift parrot population from a roughly equal number of male and female birds to three males to every female.
Females are at more risk from sugar gliders because the marsupials attack their tree-hollow nests while the females are incubating their eggs.
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