Date: April 12, 2016
Source: The University of Montana
In groundbreaking new work, Natalie Wright, a postdoctoral fellow at the University of Montana, has discovered a predictable trend in the evolution of bird shape.
Her research showing that birds on islands have evolved toward flightlessness was published April 11, 2016 in Proceedings of the National Academy of Sciences. Her partners include Christopher Witt of the University of New Mexico and David Steadman of the University of Florida.
"The search for general trends in evolution of animal shape, size and color, often comes up empty," Wright said. "Evolution tends to be unpredictable, leading toward different forms in different places. So it was gratifying to discover this trend among island birds."
Wright said it is widely known that particular types of birds tend to become flightless after they colonize islands that have no predators. Flightlessness has evolved over a thousand times, but it tends to evolve only from certain types of ancestors -- usually birds such as rails that already spend most of their time on the ground.
Wright wanted to know whether there are predictable evolutionary trends that apply to all island birds, the vast majority of which can still fly. Like the flightless species on their islands, they generally have fewer predators than their relatives on the mainland. But most species still need to fly in order to find food. So as part of Wright's doctoral research at the University of New Mexico, she focused on how flying birds evolved on islands and whether they exhibit similar changes to those seen in flightless island species.