The indigo bunting can trace it roots 45 million years back to Australasia.
Singing in the land down under: new discovery puts songbird origin in Australasi
new discovery puts songbird origin in Australasia
By Deane Morrison
Published on August 1, 2004
That male cardinal singing his heart out in your backyard has ancestors that left the neighborhood of Australia millions of years ago. Keith Barker of the University of Minnesota's Bell Museum of Natural History led a comprehensive study of DNA from songbirds and their relatives that shows that these birds, which account for almost half of all bird species, did not originate in Eurasia, as previously thought. Instead, their ancestors escaped from a relatively small area--Australasia (Australia, New Zealand, and nearby islands) and New Guinea--about 45 million years ago and went on to populate every other continent except Antarctica. The study was published online recently in the journal Proceedings of the National Academy of Sciences.
The ancestors of all songbirds escaped from a relatively small area--Australasia (Australia, New Zealand, and nearby islands) and New Guinea--about 45 million years ago and went on to populate every other continent except Antarctica.The birds in question belong to the group called Passeriformes, or perching birds. It includes all songbirds, such as robins, cardinals, blackbirds, house sparrows, house finches, and crows. 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. The true songbirds themselves are currently divided into two groups: Passerida (3,477 species, among them many familiar backyard species) and Corvida (1,103 species, including crows and ravens). The two groups of true songbirds were thought to have separate origins--the Corvida in Australasia and the Passerida in Eurasia. The Passerida then supposedly spread from Eurasia to Africa, Australasia, and the New World. But in examining the DNA sequences Barker and his colleagues made a startling discovery. "It was thought that the Passerida arose in Eurasia about 40 million years ago," said Barker. "But we found that these birds fall into a group within the Corvida. That means all songbirds trace their origins to Australasia and New Guinea." 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 said. Around 45 million years ago, the ancestors of the Passerida dispersed to Asia-over more than 600 miles of open ocean--long before the tectonic plates under these two land masses began to approach one another. For some reason, however, ancestors of the Corvida didn't leave Australasia and New Guinea until about 25 million years later, or 20 million years ago. 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. "There are many endemic Corvida birds on the Indonesian island of Lombok but very few on Bali, the next island to the west," said Barker. "And, sure enough, the line separating the Asian plate from the Australasian plate runs between Bali and Lombok."