Island Birds Can Adapt to Predators, Study Suggests

June 9, 2008

An island bird in New Zealand is able to change its nesting behavior to outwit predators—offering a ray of hope for island species worldwide facing threats from exotic invaders—researchers have discovered.

Melanie Massaro, a biologist at the University of Canterbury, and her co-authors found that New Zealand bellbird mothers spend longer periods of time on their nests when the risk of predation rises.

Both male and female bellbirds also make fewer trips to and from the nests, which reduces activity that might draw predators' attention.

Although the research focused on a single New Zealand bird, the conclusions suggest that island birds worldwide may be able to adapt to predation, the authors say.

The new study flies in the face of a widely accepted theory that suggests that island birds are especially vulnerable to predators because they've missed the opportunity to evolve alongside them, unlike their mainland counterparts.

"The main findings of our study are that naïve endemic island birds are not necessarily trapped by their evolutionary history as is generally considered to be the case, but they have the ability to change their behaviors in ways that appear adaptive," Massaro said.

"More importantly, our study demonstrates that such a change can occur over an ecologically relevant time scale of years and not centuries."

The work appears in this week's online journal PLoS ONE.

Island of Opportunity

The introduction of predatory mammals such as rats, cats, and weasels to oceanic islands has caused the extinction of many native birds. On New Zealand, casualties have included huias, piopios, and bush wrens.

The study authors point out that exotic predators threaten the survival of a quarter of the world's remaining endangered bird species.

(Related: "Alien Possums Gobbling New Zealand Forests, Birds" [April 25, 2006].)

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