Migrating birds have lighter-coloured feathers to keep them cool

Image source, Reuters

Image caption, Cattle egrets in Egypt migrate every year

Scientists have discovered that migratory birds have paler feathers to help them keep cool when flying during long journeys.

Many species of birds fly across the world - or 'migrate' - every year to find the best places to eat, breed and look after their chicks.

They can travel thousands of miles, but often face the risk of overheating if they spend too much time flying in the sun.

A new study from the Max Planck Institute for Ornithology in Germany suggests that many migratory bird species have lighter-coloured feathers to help keep them from getting too hot.

Image source, John Walton

Image caption, Around 4,000 species of birds are migrants including these Geese flying across London's' Richmond Park

Lead researcher Dr Kaspar Delhey said: "Lighter surfaces absorb less heat than darker ones, as anybody wearing dark clothes on a sunny day can attest."

"This would be particularly important for long-distance migrants that undertake extensive flights during which they cannot stop to rest in the shade.

The researchers found that nearly all birds that migrate tend to be lighter coloured than non-migratory species.