Early feathers evolved for insulation and display were barely strong enough for gliding, says report in journal Science

The first birds to make a mark in the evolutionary record might have sported an impressive plumage, but they would never have got off the ground, scientists say.

An examination of fossilised feathers belonging to the ancient birds Confuciusornis and Archaeopteryx shows their wings were too weak to support the birds in flight.

At the very best, the creatures might have used their wings to glide between trees or from vantage points to lower ground, researchers report today in the journal Science.

Robert Nudds and Gareth Dyke, at the universities of Manchester and Dublin respectively, took measurements of the feather structure of Confuciusornis, which lived in the early Cretaceous 120m years ago, and Archaeopteryx, considered to be the first bird species to emerge on Earth in the Late Jurassic, around 145m years ago.

The scientists found that the central shafts of the birds' feathers, which give wings their strength, were thinner than those of modern birds.

When the researchers calculated the forces acting on the birds' wings in flight, they realised that even if the shafts had been solid, they would barely be strong enough to allow the birds to glide. The finding suggests that powered flight arose later in birds' evolutionary history.

Archaeopteryx is believed to be a transitional form between reptiles and birds. Unlike modern birds, it had a full set of teeth, a long bony tail and three claws on each wing, which it probably used to grasp prey and cling to trees. It was the size of a small chicken.

Paleontologists have long debated whether Archaeopteryx used its wings for flight, insulation or display. The latest study suggests that feathers evolved as a means of keeping warm, before being co-opted for flight.

Confuciusornis was a crow-sized bird that had a small triangular snout and, unlike Archaeopteryx, lacked any teeth. Fossilised remnants of the birds are among the most common found in the Liaoning deposits in China, suggesting they may have lived in large colonies on the shores of the ancient lake.