Bowerbirds are the first known nonhumans to cultivate plants for use other than food.
The flashy birds propagate fruits used as decorations in their elaborate sexual displays, according to a paper published today in Current Biology.
Male bowerbirds appear to have the green thumb, as researchers discovered that these avians had an unusually high number of fruit-growing plants around their bowers. The scientists then noticed that the amorous males use the flowers to woo available females.
This would be on par with a human male not only presenting his gal with flowers, but growing them too, and then presenting the garden to her.
It remains a mystery as to whether or not bowerbirds intentionally cultivate the plants, though. The researchers think it's possible that the pretty flowers grow around their bowers due to the birds gathering fruits for display, so the gardens might offer the birds an unintended benefit.
"Until now, humans have been the only species known to cultivate plants for uses other than food," lead author Joah Madden was quoted as saying in a press release. "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."
"We do not believe bowerbirds are intentionally growing these plants, but 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," Madden continued.
Native to Australia and Papua New Guinea, bowerbirds are well known for their unique courtship behavior. The ornate bowers may be considered as art with perspective, given that the male creates his "stage" such that he looks as big and mighty as can be, even if some of it is illusion.
For this latest study, the research team observed bowerbirds in Taunton National Park, Central Queensland. They found higher numbers of Solanum ellipticum, or potato bush, plants around bowers than in other locations. These plants have bright purple flowers and green fruit. Their research showed that the birds were not selecting locations with a high number of the plants, but rather that they were growing plants around their bowers.
It's a gorgeous plant, as you can see from images like this one.
Bowers with many fruit on them are especially attractive to choosy females. Males collect the fruits, but when the fruits shrivel, they discard them nearby. This results in seeds germinating in the ground around the bower. Bowerbirds clear the area around their bower of grass and weeds, making ideal conditions for new plants to germinate. (Wouldn't you like to have one in your garden?)
Male bowerbirds can maintain a bower in the same location for up to 10 years and thus benefit from establishing plants that may survive for several years.
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.