Where do storks come from, mommy?

Where do storks come from, mommy?

Surprisingly, condors and other New World vultures are much more closely related to storks than to Old World vultures, according to recent studies of these species's DNA molecules. Over the last 10 years, Charles G. Sibley and John E. Ahlquist of Yale University have developed a system of classifying birds by the similarities in their genetic material. They have analyzed more than 25,000 DNA samples from about 1,600 bird species, using techniques that are also being applied to primate classifications (SN: 6/9/84, p. 361).

The researchers find that DNA evolution occurs at the same average rate in most bird species, so it can provide a measure of when species diverged. The bird family tree proposed by Sibley and Ahlquist disagrees in several of its branches with previous classifications based on the anatomical similarities, but it fits well with geological data, Sibley says.

"Anatomical characteristics are shaped by functional requirements and may provide false clues about the history of a species' evolution,' Sibley says. "Swifts and swallows, for example, are superficially alike because both groups are specialized to feed on flying insects.' But the DNA comparisons indicate that they are not closely related. The swifts are more closely related to hummingbirds, and the swallows are classified among the songbirds.

Perhaps the most surprising DNA finding, the scientists say, is that starlings, which have been considered to be relatives of crows, are related instead to mockingbirds, from which they evolved 25 million years ago. Sibley says, "This correlates with the belief that the two species evolved from a common ancestor that lived in northern Canada and Greenland until temperatures cooled about 25 million years ago and forced birds and animals south to Europe and America.'