Flying needs sharp eyesight. Birds have to twist and change direction in an instant to dodge enemies, avoid obstacles, catch prey or just keep up with the flock.
A bird’s big eyes take up more space in the skull than its brain does. They are fitted tightly into its head – which is why birds need to move their heads to see, instead of their eyes.
Some birds have many more light receptor cells (called rods and cones) in their eyes than we do. This gives them sharper eyesight than ours. A buzzard can see 8–10 times farther than we can, and spot its prey from three kilometres away.
Birds can also see colours better than we can. This is why many have developed such colourful plumage to impress each other – or complicated patterns to hide from each other.
Most birds have eyes on the side of their head, which gives them a wide field of view. A pigeon can see for 320 degrees without turning its head. This helps it to look out for danger and know where its flock is at all times. Some birds, such as woodcocks, have eyes set far back on their head, so they can keep looking out while their head is bent down feeding.
But birds of prey and owls have their eyes in front – just like cats and other hunters. This restricts their field of view, but it gives them a secret weapon: binocular vision. Binocular vision is when both eyes can focus on one thing at the same time. It makes it much easier to judge distances, which is vital when chasing prey.