The Critically Endangered swift parrot is in rapid decline. While females are sitting on eggs or chicks within nesting tree hollows, they are highly vulnerable to predation by sugar-gliders. Predation of nesting females has led to biased sex ratios. It is estimated that fewer than 1000 individual swift parrots remain, and overall 73% are estimated to be male. This project investigaed the implications of this sex bias on the persistence of the swift parrot population.