Hazel Jackson, University of Kent
Dear Thomas and Luke,
Thanks for your question. First of all, I should mention that not all birds have their eyes on the sides of their heads. Pigeons and parrots do, but other birds, such as owls, have large eyes placed close together at the front of their heads – a bit like ours.
Whether they have eyes at the front or on the sides of their heads, all birds can still see straight ahead. But that doesn’t mean all birds see things in the same way. In fact, where a bird’s eyes are on its head can tell us a lot about how it sees the world.
Having two eyes means animals can see a three dimensional image of what’s around them. So they can perceive the height, width and depth of an object, as well as how far away it is.
Where a bird’s eyes are on its head affects its field of vision – that’s how much it can see in front and to the side at any one time. Think about how far you can see to either side without turning your head: these are the limits of your own field of vision.
Because owls have eyes at the front of their heads, they have a smaller field of vision – around 150 degrees for a barn owl (though they can turn their heads very far to look around).
Parrots, pigeons and other birds with eyes on the sides of their heads have a much bigger field of vision, of about 300 degrees. Amazingly, this means that they can see in front and a long way to the side, at the same time.
Where the eyes are placed decides how a bird views its surroundings using different types of vision. Binocular vision means both eyes focus on the same object at the same time, and eye movement is coordinated – this is the kind of vision that predatory birds such as owls rely on most.
Monocular vision means each eye is focused on a different object at any particular moment, and this is normal for parrots and pigeons. Having different kinds of vision helps different kinds of birds survive in the wild.
For parrots and pigeons, having eyes on the sides of their heads is a huge advantage. Having a wider field of vision with only a small blind spot behind them lets these birds see where they are going, while also keeping an eye out for predators which might be trying to sneak up on them.
For predatory raptors such as barn owls, having forward-facing eyes helps them to see depth and distance much more clearly, since both eyes can focus on the same object at the same time. This is perfect for spotting and catching small prey such as field mice.
So though it might seem like birds with eyes on the side of their heads can’t see where they are going, they can see forward and sideways at the same time, and in fact can see much more than those with eyes facing forwards.
Hazel Jackson, Affiliate, University of Kent
This article is republished from The Conversation under a Creative Commons license. Read the original article
Stay updated with all the insights.
Navigate news, 1 email day.
Subscribe to Qrius
