Did You Know... About Bird Eyes?

Seagull wearing a bow tie with a pencil stuck behind the feathers on its head

By History and Science Reporter Bill Quill

Recently I’ve been learning about my distant cousins who fly north in the summer when it gets hot and south in the winter when it gets cold. These migrating birds just seem to know how to find the right direction to fly. I am sure they use their eyes to see landmarks, such as city parks and mountains. But it also seems that they can somehow sense which way is north or south. Humans find directions by looking at a magnetic compass needle which is moved by Earth’s magnetism and always points to the north and south magnetic poles. But a migrating bird doesn’t carry a compass.

Well, some curious human scientists think they have discovered how my migrating cousins know which way is which. It seems the birds have a unique molecule in their eyes that is sensitive to the Earth’s invisible magnetism (a molecule is a very very small part of something). Scientists think that birds can just look ahead and tell which way is north (or south) and fly in that direction.

Do you ever notice how humans sometimes wear sunglasses that are dark at the top of the lens but get slowly lighter towards the bottom of the lens? It probably helps humans safely look at where they are stepping on the ground. The human scientists have found that this may be similar to how my migrating cousins “see” north. The molecule in their eyes, which is affected by the Earth’s magnetism, may make their eyes see parts of the world lighter and other parts darker, like those sunglasses, which helps guide them to the north or south!


Illustration: © Fiona Carswell, 2021.