File photo: A palaeontologist shows the cranium of a bird, from the Pelagormithidae family.

London - Feathers initially evolved to keep birds warm rather than to let them fly, a study said on Thursday.

Researchers found that the feathers on birds’ dinosaur ancestors were arranged in multiple layers to act as insulation and preserve heat.

It was not until millions of years later that they began to evolve for display and camouflage – and then finally to allow the animals to fly.

The study, by the universities of Bristol, Yale and Calgary, found that prehistoric birds had rigid layers of feathers which could be used for limited gliding.

These evolved into highly effective feathered wings which could rapidly change their shape, span and area.

Dr Jakob Vinthers, of the University of Bristol, said: “This is shedding light not just on how birds came to fly but more specifically on how feathers came to be the way they are today.” - Daily Mail