Sydney:Endangered Purple-crowned Fairy-wren female birds call the shots or tune when it comes to breaking-up with their partner, according to a new study. The study, published in the journal Behavioral Ecology, revealed how the researchers studied 317 breeding pairs to learn what was driving the behaviour and highlighted on the causes of divorce in the monogamous year-round territorial birds. As many as one in five avian pairs ended in divorce over nine years and the researchers were surprised to find that it was the females who were more likely to break up. The research shows how important is high-quality habitat for these birds and to what extend they will go to secure a top post. "Females exhibit long-term planning and are more likely to end their relationship when the opportunity for a better territory arises. We found females were prepared to wait, sometimes up to three years, for a good vacant spot to come up -- where the female owner has died or moved on," said Anne Peters, Associate Professor, Monash University. Found in Western Australia's Kimberley region, it's estimated that less than 10,000 Purple-crowned Fairy-wrens remain in the area. "These females are sitting there, they're not happy with their partner or their territory; they have an affair on the side and they're more likely to divorce. With divorce, they get a different partner and a different territory. The territory seems to be more important than the partner," added Peters. According to the researchers, the females were prepared to take drastic action to gain a better territory and divorce is a female strategy to improve reproductive success in the long-term and the immediate benefit is a better territory. The endangered bird lives in a harsh, unpredictable environment where 80 per cent of nest attempts end in failure, so females are prepared to divorce for a better territory because a good site for nesting will pay off, revealed the study.