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American Association for the Advancement of Science

No flap: Earliest birds were poor flyers

This is a life reconstruction of the earliest fossil bird, Archaeopteryx.
Artwork by Todd Marshall]

The ancient birds Archaeopteryx and Confuciusornis weren't flapping flyers and were gliders at best, according to a new study of the birds' fossil feathers.

To support powered (flapping) flight, birds' feathers must be strong enough to support the birds' weight without breaking or bending. In modern birds, this strength comes from the central shaft, which stiffens the feather along its length. The shaft is hollow, to make the feathers lighter.

Robert Nudds of the University of Manchester in England and Gareth Dyke of University College Dublin in Ireland carefully measured and analyzed fossil feathers from Archaeopteryx, which lived in the Late Jurassic period about 140 million years ago, and Confuciusornis, from the Early Cretaceous, about 100 million years ago.

This is one of the specimens of Confuciusornis sanctus included in the study. The approximate length of one functional primary feather is marked with a black line. Scale bar is 20 mm.
Image courtesy of Science/AAAS

They found that the central shafts of Archaeopteryx and Confuciusornis feathers were thinner than those of modern birds. They calculated the various forces acting on the feathers during flight and determined that even if the shafts had been solid, they still would have been just barely strong enough to allow gliding.

Powered flight probably arose later in birds' evolutionary history, the scientists have concluded. Their study appears in the 14 May issue of the journal Science.