Three kagu birds standing on a log

Adult male kagus routinely make contact with their parents, some of whom receive daily visits from their sons. Credit: Roland Seitre/NPL

Animal behaviour

Unconventional lifestyle found in island bird

Kagu brothers have surprisingly close bonds, with each other and their parents.

A flightless tropical bird has a social life previously seen only in human populations: brothers live together, share a mate and stay in touch with their parents.

Jörn Theuerkauf and Roman Gula at the Polish Academy of Sciences in Warsaw and their colleagues used radio tracking to monitor populations of kagu (Rhynochetos jubatus) on the Pacific island of New Caledonia. They found that the birds breed in small groups belonging to larger family clans. Genetic analysis of the birds’ feathers showed that the groups include between one and three brothers or half-brothers, and a single unrelated female. Until now, this social structure has been recorded only in some human populations — for example, in Bhutan.

After starting their own group, males regularly returned to visit their parents, another behaviour previously seen only in humans. All the members of a group care for chicks, which leads to better survival rates than in two-parent families, the authors say.