Stay at home sons - why cutting out the cooking could get rid of the kids

November 23, 2005

It's become a common modern phenomenon - kids are leaving it later and later to leave home. But for any frustrated parent out there help may be at hand - birds may have the answer to kicking the cuckoos out of the nest. Scientists at the University of Exeter in Cornwall and the University of California, Berkeley have shown for the first time that male birds will only stay at home if they think their parents are wealthy enough.

In a paper, published in Proceedings of Royal Society B, Dr Andy McGowan, currently at the University of Exeter in Cornwall, and Dr Janis Dickinson from the University of California, Berkeley looked at the make-up of western bluebird family groups in California, for whom wealth comprises clumps of mistletoe. These birds are highly territorial vigorously defending their mistletoe, which provides an essential food source during harsh winter months.

Dr McGowan and the team created different sets of territories by removing half the mistletoe in some areas whilst leaving others intact. In areas where the mistletoe continued to flourish 50% of sons stayed with their parents compared with only 8% of sons in areas where mistletoe had been removed. Daughters on the other hand seem to pay no attention to the wealth of their parents and leave home anyway.

"This is the first time it's been shown experimentally that resources cause offspring to stay at home and strongly supports the idea that wealth is the starting point for the evolution of kin-based sociality. It wasn’t that an absolute insufficiency of resources was causing sons to leave but the relative wealth of the parents. Western bluebird sons seem to be assessing just how wealthy their parents are and if it does not come up to expectations then they leave, probably because they think they can do better on their own elsewhere. The findings from this study really help expand our theoretical understanding of the evolution of human social behaviour."

Source: University of Exeter