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If you were to stand face to face with an owl, after a while it would start to move its head,

bobbing rhythmically from side to side then forward then back, or almost completely upside down.

All while still looking at you with its body still facing the front.

Is the owl trying to communicate something? Is this perhaps some kind of dance?

All these varied head movements help the owl judge the position and distance of things around it,

essentially to triangulate on objects, including potential prey.

And to build a composite picture of its surroundings, this head bobbing helps make up for an anatomical limitation.

An owl's eyes are fixed in position, they simply can't move the way our eyes do.

So to look up down or to the side, an owl has to move its head.

They have very flexible necks, and can do three quarters of a full head turn,

looking over one shoulder around the back and almost over the opposite shoulder.

And after a few of these head bobs to triangulate on their prey, they rarely miss.

It's not only owls that measure the world this way, most other birds of prey like falcons and hawks have this same intent fixed predator's eyes.

And so they, too, perform their share of head bobs, figuring out what's what and what's where.

For Bird Note, I'm Mary McCann.

Bird Note gives you the sounds of birds every day, and you get the sights as well when you follow us on Instagram at Bird Note Radio.