In total darkness an owl has no better ability to see than any of us. However, 100 million years of evolution allows this group of birds to squeeze enough light out of their nocturnal world to enable them to hunt, which they do as effectively as any other predator. Owls’ reputation for being able to see well at night is richly deserved.
Owls’ eyes are packed tightly with light receptors (known as rods). This allows owls the power of vision in extremely dimly lit locations. Owls that are the most nocturnal, such as the widespread tawny owl, have the highest number of rods in their retinas. Owls can also see well in daylight because their irises can close tightly, allowing only a tiny amount of light to pass.
Like us, owls have forward-facing eyes, giving them exceptional binocular vision. This permits them to focus on a smaller area – a little like focusing the beam of a torch – but it also allows them to judge distances well: a vital trait if you have to pluck prey from the woodland floor in moonlight.
Highly developed eyes give these birds the edge in most situations, but there are times when even an owl is blind. Then, like a fi ghter pilot, owls switch to other systems to locate their targets. Slightly nonsymmetrically placed ears allow owls to find prey by listening when sight alone is not quite enough. Tests have shown that owls can successfully pounce on a mouse that is under inches of snow or in complete darkness.
From the Arctic wastes to the searing deserts there are few places on earth that doesn’t have at least one of these impressive night-shift hunters. However, many owls are threatened, proving that a history 30 times longer than man is not enough to combat the threats these birds now face.
