24 April 2012

Bowerbirds gardening for pleasure

by Will Parker

Scientists say they have uncovered the first evidence of a non-human species cultivating plants for use other than as food. The researchers, from the Universities of Exeter (UK), Postdam (Germany), Deakin and Queensland (Australia), report in the journal Current Biology how bowerbirds grow fruits to be used as decorations in their sexual displays.

Native to Australia and Papua New Guinea, bowerbirds display unique courtship behaviors where the males build ornate bowers and decorate them with scavenged, brightly-colored objects in order to attract females.

Observing bowerbirds in Taunton National Park (Central Queensland), the researchers found higher numbers of potato bush (Solanum ellipticum) plants around bowers. These plants have bright purple flowers and green fruit. Their observations indicated that the male birds were not selecting locations with a large number of plants, but rather that they were growing plants around their bowers.

The study explains that bowers with lots of fruit on them are especially attractive to choosy females. When the fruits shrivel, the male will discard them nearby which results in the seeds germinating around the bower. Male bowerbirds can maintain a bower in the same location for up to ten years, so they can reap long-term benefits from establishing plants that may survive for several years.

The researchers found that, like farmers selecting for fatter pigs or larger seeds, the bird's behavior may lead to a change in the appearance of fruits. The fruits from plants close to the bowers were slightly greener in color than those found on other plants. The researchers tested the males' choices and found they preferred this color to that of the other fruit.

"Until now, humans have been the only species known to cultivate plants for uses other than food. We grow plants for all kinds of things - from drugs, to clothing, to props that we use in our sexual displays such as roses - but it seems we are not unique in this respect," noted lead researcher Joah Madden, from Exeter University. "This accumulation of preferred objects close to a site of habitation is arguably the way any cultivation begins. It will be very interesting to see how this mutually-beneficial relationship between bowerbirds and these plants develops."

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Source: University of Exeter