World's Songbirds Share Common Australasian Roots

MINNEAPOLIS, Minnesota, July 21, 2004 (ENS) - All songbirds trace their origins to ancestors who left Australasia and New Guinea some 45 million years ago and went on to populate every other continent except Antarctica, scientists report.

The finding undermines the previously held belief that these birds, which together account for almost half of all known bird species, originated from Eurasia.

The study, led by Keith Barker of the University of Minnesota's Bell Museum of Natural History, will be published online this week in the journal "Proceedings of the National Academy of Sciences."

Cardinal in the Morton National Wildlife Refuge, Rhode Island (Photo by John and Karen Hollingsworth courtesy USFWS)

The group is further divided into birds that must learn their songs "true songbirds" and those with the innate ability to sing the "correct" song.

True songbirds account for 4,580 of the 6,000 known Passeriformes species and are currently divided into two groups - Passerida and Corvida.

The Corvida group, which consists of 1,103 species, including crows and ravens, was though to have originated in Australasia - an area that consists of Australia, New Zealand and nearby islands.

But the Passerida group, which includes 3,477 species, among them many familiar backyard species, was thought to have originated in Eurasia.

The Passerida then supposedly spread from Eurasia to Africa, Australasia and the New World.

But DNA evidence shows otherwise, Barker and his colleagues report.

Crows in an Oregon garden (Photo courtesy University of Oregon)

The Passerida differ from the Corvida because the Passerida somehow made it out of Australasia and New Guinea and onto the Asian mainland long before the Corvida, Barker explained.

Asia and Australasia are carried on separate plates in the Earth's crust, and for many millions of years those plates were far apart.

Some 45 million years ago, the ancestors of the Passerida dispersed to Asia-- across more than 600 miles of open ocean - long before these two plates approached one another.

For some reason, however, ancestors of the Corvida did not make it until about 25 million years later, or 20 million years before today.

At that time, Asia and Australia were much closer to each other, and island chains that could have allowed the Corvida ancestors to "island hop" to the mainland appeared, Barker said.