'Monogamous' gannets are more unfaithful than humans

Australasian gannets, once thought to mate for life and held up as a role model for humans, have been found "divorcing" each other.

A German doctorate student, Steffi Ismar, 29, has completed two years of research on the Cape Kidnappers colony in Hawke's Bay. She found 40 per cent of the birds abandon their partners each breeding season.

"It's always been assumed that these birds are monogamous," she said. But gannets are less monogamous than humans – figures from 2008 show a divorce rate among New Zealanders of 11.3 per cent.

Ms Ismar's research, as part of an Auckland University team, also showed birds that parted and found a new mate were less likely to raise a chick in their first breeding season than those who stayed with their partners. Birds taking up with new partners probably needed to learn how to work together, she said.

"Gaining experience of how to co-operate with a new partner may be the critical factor in ensuring that adults can successfully raise their young."

She could not tell if it was male or female birds that were more likely to push the other partner out. The birds look identical and sexing requires blood sampling. She plans to do that in a future study.

All is not lost, however, in the world of avian romance: swans and the wandering albatross were still thought to form life-long pairings, Ms Ismar said.

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