Early Birds Were not Very Ecologically Diverse

Birds come in astounding variety—from hummingbirds to emus—and behave in myriad ways: they soar the skies, swim the waters, and forage the forests. But this wasn't always the case, according to research by scientists at the University of Chicago and the Field Museum.

The researchers found a striking lack of diversity in the earliest known fossil bird fauna (a set of species that lived at about the same time and in the same habitat). "There were no swans, no swallows, no herons, nothing like that. They were pretty much all between a sparrow and a crow," said Jonathan Mitchell, PhD student in the Committee on Evolutionary Biology, and lead author of the new study, published May 28, 2014, in Proceedings of the Royal Society B.

The scientists examined a group of bird fossils dating back to the Cretaceous period, around 125 million years ago, relatively soon after the emergence of birds. The fossils were collected from an area in China where there was once violent volcanic activity, leading to a plethora of well-preserved fossils as intermittent eruptions periodically killed many birds. The researchers examined the diversity of species in this sample. However, because fossils indicate only the physical characteristics of the birds, understanding the diversity in how the birds behaved required significant scientific legwork.

To tease out the ecological roles played by the prehistoric birds, the researchers used modern-day birds to build a statistical technique that could relate the physical characteristics of a bird to its diet, behavior and habitat. Long legs might be associated with birds that wade through water, for instance, and the shape of the beak might hint at what the bird ate. For this purpose, the scientists painstakingly measured 1,400 modern birds—mostly from the Field Museum's collections—and extracted the correlations between these measurements and the birds' behavior.

link.

paper link.