25 July 1999

Protective fathers raise sexy sons

by Kate Melville

According to Australian scientists, attractiveness is less about genes and more about environment, in particular the housekeeping abilities of your father - at least, that's how it is for sparrows.

University of Queensland Zoology and Entomology Department lecturer Dr Ian Owens was part of a research team examining the behavior of 100 house sparrows on Lundy, an island in the Bristol Channel off the United Kingdom.

Marked for identification and nested in artificial boxes, male sparrows were observed for their chick-rearing abilities and young males for the size and condition of sexual ornaments known as "badges" — a bib of black feathers beneath their beaks.

"In many animals, males have what evolutionary biologists call 'sexual ornaments' — features no good for improving survival but used when displaying to females. The showy plumage of male birds-of-paradise or peacocks are a good example," Dr Owens said.

"It was previously thought females chose males with the best plumage because this signalled the male had a good supply of quality genes for the next generation."

However, in a controversial finding, recently published in Nature, the researchers found that the best badges in sparrows were actually determined by environmental rather than genetic factors, in particular how effective fathers were at keeping nests free of parasites and other males from "beating up" their offspring.

"We performed a series of cross-fostering experiments in which we moved chicks between nests so that each chick had a foster father as well as its biological father. We found there was a strong resemblance between sons and their foster fathers but no resemblance at all between sons and their biological fathers," Dr Owens said.

The most protective fathers - those that kept other birds from 'bullying' their sons - and the tidiest fathers - those that picked nest boxes free of parasites such as ticks and fleas - raised sons with the best badges, he said.

"Other birds can damage the badges while parasites either chew the badges off or suck the bird's blood, making them weak and reducing the badge's condition," Dr Owens said.