New Zealand women may think the man drought is bad, but it is nothing compared to what it was like for the moa.

New research by a team at Canterbury University has found that adult male moa were heavily outnumbered, apparently because the females were such bullies.

"Using high-end ancient DNA technology, we genetically sexed 227 moa and found that females outnumbered males by 5 to 1," said project leader Professor Richard Holdaway, of the university's School of Biological Sciences.

"Analysis of ancient DNA from several dozen stout-legged moa - one of four moa species under scrutiny - showed that immature males were as common as females, but as adults they made up only a quarter of the population.

"It seems likely that female moa were giving the boys a hard time - perhaps being territorial and excluding males from the best habitat."

Like the flightless Cassowary bird in Australia, the moa's "home ranges" and best feeding grounds would probably have been controlled by the female, who would allow in the males once a year or so, Professor Holdaway said.

If females, twice the body mass of the male, did not want the blokes around, all it would take was a turn of the head or a certain sound to get the message across. And being 50 per cent taller, the female could also reach fruit and vegetation to feed on that the males could not.

The research was carried out on fossil remains from two North Canterbury sites, both of which date to just before Polynesian settlement.

PhD student Morten Allentoft amplified DNA from more than 260 of the extinct birds.

Mr Allentoft said: "The fact that we could extract nuclear DNA from most of these bones opens up many new possibilities in ancient DNA research and offers high-resolution genetic insights into moa population biology.

"Uncovering these crazy sex ratios is just the beginning".