Some ovenbird species make nests lined with grass or snake skin, others adorn their homes with elaborate domes or awnings. From the array of domestic styles, researchers have deduced the likely order of branchings of this common bird's family tree.
Ovenbirds are a family of small bug-eaters that live in the Neotropics, from the sand dunes of Chile to the mountain forests of Mexico. Throughout their range, the 240 recognized species construct enclosed nests, where eggs incubate in the dark, safe from weather and predators. Beyond that the birds diverge: Different species have perfected the art of enclosure with myriad forms and resources.
Ornithologists Krzysztof Zyskowski and Richard Prum of the University of Kansas, Lawrence, thought that this "startling diversity of nest types" might help them sort out the hitherto murky ovenbird family tree. They analyzed 24 nest characteristics, including shape, material, and building behaviors--such as tree-hollowing, leaf-stripping, or plant-macerating--looking for common materials or methods shared by different species that would point to a recent common ancestor.
Their analysis paid off, they report in the October issue of The Auk, in the first formal ovenbird family tree. For example, the best-known ovenbird, Furnarius, builds ovenlike mud domes atop fence posts and trees throughout South America. That bird was believed to be related only remotely to other genera that nest in earthen burrows. But Zyskowski and Prum found that the linings of both species' nests are cup-shaped and composed of layers of grass and strips of inner bark. They concluded that Furnarius evolved from a lineage of earthen cavity nesters.
"Previously, most people would have said that nests are too plastic to provide evidence of evolutionary relationships," says Robert Zink, an ornithologist at the Bell Museum in St. Paul, Minnesota. Zyskowski and Prum, he says, "have paved the way for using this sort of evidence in phylogenetic studies of other groups."