This study, conducted by Rene Duckworth, Ph.D., suggests the birds may play more active roles in their own natural selection than traditional models of evolution would support.
"The traditional view of evolution is that organisms are passive creatures on which natural selection operates," said Duckworth, who just completed her doctoral training at Duke. But her research results, published online on Wednesday, April 12, 2006, in the journal Proceedings of the Royal Society B, suggest a different model, at least among these bluebirds.
"By selecting the environment in which they live, animals can actively affect the natural selection they experience," Duckworth said in an interview. "The main message of this study is that the ability of organisms to choose their environment needs to be made a more explicit part of evolutionary theory."
In her studies, funded by the National Science Foundation, Duckworth followed up on previous findings that adult western bluebirds aggressively defend large breeding territories and also use different foraging strategies in wooded and open habitats.
In gathering worms and insects to feed their young, birds living in wooded environments "mainly forage by perching on trees to scan the ground for prey," Duckworth said in her article. But in open areas with few trees, the birds must be agile in order to "hover or hop along the ground to search for prey."
Despite such advance knowledge about behavior, "the relative importance of behavior in driving or inhibiting evolutionary change remains largely unresolv
Contact: Monte Basgall