Raising young in nuclear family groups – evolutionary bliss for some birds
In a new study, researchers at Lund University and Oxford University examined how the world’s different bird species raise their offspring. The study focused on some 200 species that raise their offspring in collective groups comprising three or more individuals. Of these, around 150 species raise their young in family groups in which one or more older siblings have stayed with the flock, whereas some 50 species form groups of unrelated individuals that aggregate during the breeding season. The results, now presented in the research journal Nature Ecology & Evolution, are striking.
“The species that raise their young in family groups have developed larger, more complex groups with specialized division of labour, like that of bees and ants. This is completely lacking in species where individuals without family ties form groups”, says Philip Downing, biology researcher at Lund University.
The species that raise young collectively in family groups evolved a greater ability to carry out different tasks – some individuals focus on reproduction, while others care for the young. This division of labour has not evolved in groups that lack family ties, instead all the individuals focus on reproduction.
“Our results help us to understand why the social groups of species remain relatively simple whereas others have taken the path to greater group complexity”, says Philip Downing.