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. Asia and Australasia are carried on separate plates in the Earth's crust, and for many millions of years those plates were far apart. Around 45 million years ago, the ancestors of the Passerida dispersed to Asia--over more than 600 miles of open ocean--long before these two plates approached one another. For some reason, however, ancestors of the Corvida didn't 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.
"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."