Early bird species such as Archaeopteryx would probably not have been able to flap their wings, new evidence suggests.

Archaeopteryx, which lived 140 million years ago, looked like a feathery dinosaur with wings and is considered to be the first true bird.

But there is a lot of controversy over whether the creature was capable of powered flight. The research indicates that, at best, Archaeopteryx would have been a glider.

Fossil studies revealed that Archaeopteryx feathers had thinner shafts than those of modern birds.

A team led by Robert Nudds from the University of Manchester carried out calculations which showed that the feathers would have been too weak for flapping wings.

In fact they were only barely strong enough to support gliding from tree-to-tree.

The same was true of Confuciusornis, a later bird that lived 100 million years ago. "If Archaeopteryx and Confuciusornis were flapping flyers, they must have had a feather structure that was fundamentally different from that of living birds," the researchers wrote in the journal Science.