Domestic life of birds

Rowan Hooper, news editor

The nest of a house finch (Carpodacus mexicanus) (Image: Sharon Beals)

I REMEMBER as a kid exploring a near-derelict building on a bit of land behind a row of shops and finding a bird's nest on a dusty shelf, complete with squawking, alien-like chicks. I still remember the thrill of feeling I'd stumbled across a secret - but there was also an odd sense of intrusion, like I'd walked in on my mother getting dressed.

Both emotions are provoked by Sharon Beals's beautiful images of birds' nests. "When I hold these fragile structures in my gloved hands, all built with beak and claw, it makes me wonder at the instincts that formed them, embedded in DNA honed over millions of years," she says. Beals, who lives in San Francisco, photographed the nests from collections in museums around the US.

The nest of a western tanager (Piranga ludoviciana) (Image: Sharon Beals)

Perhaps one of the reasons that seeing a bird's nest is such an intimate experience is that it is a peek into their genes. Just as geneticists can talk about the genes that contribute to eye colour, or height, for example, they can also imagine genes that influence things further afield, outside the immediate structure of the organism, like a spider's web or a bird's nest. This is the idea of the extended phenotype, as conceived by evolutionary biologist Richard Dawkins. Bowerbirds, for example, probably have genes for selecting coloured items to decorate their elaborate bowers. Seeing a bird's nest gives you an idea about their genes, as well as their environment, in a similar way to how seeing someone's house gives you an idea about their social background. So the nest of this house finch (top picture), collected in Arizona in 1965, tells us that it used garbage to construct a home rather than natural materials.

http://www.newscientist.com/