The finding, being published in the journal Science, is part of a landmark genetic study of 169 bird species being published by Field Museum researchers, the Chicago Tribune reported Saturday.

"This is the most important single paper to date on the higher-level relationships of birds," said Joel Cracraft, curator of birds at the American Museum of Natural History in New York, who was not part of the study.

Many previous studies on birds relied on comparisons of outward characteristics and behaviors, but genetic comparisons can tell a deeper story.

The Field Museum began its five-year effort with seven other institutions to do an unprecedented genetic analysis using powerful computers.

They discovered many cases in which seemingly similar birds were merely distant relatives, or birds long assumed to be unrelated were closely linked.

Among other noted findings is that grebes, a type of diving bird, are not related to loons, as ornithologists had thought. Grebes appear closely related to flamingos, the study found.

"It's kind of crazy to us, too," said Shannon Hackett, a lead author of the study and associate curator of birds at the Field Museum.