Cultivating berries? (Image: David Kleinert)

What has green fingers but no hands? The bowerbird, if a new study is to be believed. Males appear to cultivate plants around the structures they build to attract a mate.

Male spotted bowerbirds (Ptilonorhynchus maculates) build structures, or bowers, from twigs before intricately decorating them with objects to attract a female. One of the males’ most desirable decorations is the berry of the Solanum ellipticum plant.

Joah Madden of the University of Exeter, UK, and colleagues studied the distribution of S. ellipticum in an area of Queensland, Australia, inhabited by the birds. Although the males didn’t build their bowers in locations with abundant S. ellipticum, a year after construction there were, on average, 40 of the plants near each. Birds with more plants nearby had more berries within their bowers, which Madden has previously found is the best predictor of a male’s mating success. Males may discard shrivelled berries outside their bowers.

The bowerbirds are thus shaping the distribution of the plants in the area – but is it cultivation? Madden acknowledges the results do not imply that the birds intentionally grow the plants. But he points out that some hypotheses favour similarly unintentional origins for human agriculture, suggesting the bowerbirds’ activities could just about fall under the definition.

Journal reference: Current Biology, DOI: 10.1016/j.cub.2012.02.057