As mammals age, the roots of their hair stop producing pigments, which means it will eventually turn grey. Although, for humans this is often seen as a sign of a body in decline, in some species grey hair is a positive trait that signals maturity. For example, dominant male gorillas have characteristic grey hair that covers their back and are known as silverbacks.
In the wild, most birds will never reach an age that would be considered old enough to go grey. So is this the reason that it’s rare to spot a grey bird?
It’s not. In fact scientists have discovered that birds don’t go grey because their feathers aren’t only coloured with pigments. Light bounces off protein in their feathers in different wavelengths to produce the variety of colours in birds. As birds get older they can control changes in the nano-structures of their feathers to ensure they don’t go grey and are still able to recognise each other.
If you’ve spotted what looks like a greying bird with patches of light coloured feathers, it is unlikely that this is due old age. What you’ve seen is probably a leucistic bird and these abnormalities in their feathers occur due to a genetic mutation.
