Brighter birds bag bigger territories.

Studies of closely related birds in the forests of Kashmir, India, have shed light on the role of habitat in the evolution of plumage color patterns. Birds living in dense woods tend to evolve bright patches that they keep hidden except when they want to show off to members of their species, says Karen Marchetti of the University of California, Davis.

She compared patches in warblers belonging to the genus Phylloscopus. Depending on where they breed, each species of these small greenish birds sports a different pattern, ranging from a simple wing bar to two wing bars, a stripe across the head, a patch on the rump, and white outer tail feathers.

For several breeding seasons, she examined the role of patches by dividing males into three groups. She covered up part of the wing bars in one group with green paint and enlarged the bars of a second group with yellow paint. She coated some control birds' bars with clear paint to counter any effect caused by the paint itself.

After standoffs in which neighboring males display their wing bars at close range, the brighter bird always takes a chunk of the duller bird's space, she reports in the March 11 NATURE. That also proved true when Marchetti added a crown stripe to some males, making them even more conspicuous.