Owls are amazing and beautiful birds.
Watching the ground with their big eyes.
But have you ever seen one turn its head?
How do they do that?
We finally have some answers.
Let's take a spin through owl necks.
Let's talk about why owl necks have to be so amazing.
Owls hunt at night, so they need big eyes to collect lots of light.
Large owls are only about 2 feet tall, but their eyes are about the same size as adult
human eyes.
Owl eyes aren't round.
They're shaped kind of like telescopes.
Tube-shaped eyes run along both sides of their head.
These eyes can see incredibly well in the dark, but they can't move to look at prey
animals.
The owl has to turn its entire head to change where its eyes are pointing.
And the need to look around for prey puts selective pressure on their necks.
Owls can rotate their head 270 degrees in both directions.
Turning from here around to here, or around the other way to here.
Wow!
Very, very flexible necks.
Let's just say that any of this would be really bad for a human.
But owls have at least four adaptations that help them turn heads.
First let's look at an owl's skeleton.
Looking at a fluffy, feathery owl gives you the wrong idea of what their skeleton looks
like.
Owl skeletons look really different than owls!
They have extra neck bones to make them extra flexible.
They have 14 neck vertebrae, compared to our 7 vertebrae.
More flexible joints means the whole neck is more flexible.
Second, at the top of that long neck, where the neck bones connect to the skull, there
is one pivot point around which the skull and muscles can rotate.
Humans have two pivot points that have to work together.
Here's an analogy that might help.
Spinny office chairs.
Humans are doing the equivalent of sitting in two spinny office chairs.
You can rotate, but it's limited.
Which is good, seriously.
Your neck is not built to rotate far, so you want your neck joints to limit it.
But an owl is like sitting in one office chair.
You can rotate freely on this joint.
270 degrees isn't that big a deal.
In the owl's neck it's the other stuff, the muscles and blood vessels, that run out of
slack before the pivot joint does.
Two more adaptations in the neck bones make it easier for the owl to turn its head.
We all have gaps in our vertebrae that let blood vessels pass through.
If you look at a vertebra, there would be blood vessels passing though the holes here
and here.
And the blood vessels are around the same size as the holes available.
But owls have gaps that are way, way bigger than usual.
Their vertebrae holes are ten times the size of the blood vessels passing through them.
There is a lot of empty space around each blood vessel.
So owl neck arteries can move around as needed when the neck is twisting.
Before the arteries even enter these gaps, there's some slack at the bottom of the neck.
Owl arteries enter the neck higher than they do in humans.
The slack part at the bottom of the neck is free to move around to relieve strain from
rotation.
Now let's check out the circulatory system.
The arteries in the neck send up oxygen-rich blood to the brain, eyes, all this important
equipment up here that is delicate and very sensitive to oxygen deprivation.
Owls don't have blood vessels that just go straight from the heart to the brain and back.
They have crosses and connections between different blood vessels in their heads.
The cross-connections allow blood to take alternate paths through the head even if one
artery gets pinched or twisted closed.
And finally, there are enlarged, stretchy arteries at the top of the neck.
These areas can act like blood reservoirs, storing a little bit more oxygenated blood
close to the brain so the twisted neck doesn't impact the owl's brain.
Without all these neck adaptations the owl would be very limited in what it could see,
and it wouldn't be the deadly nocturnal hunter that it is.
An owl's neck supports its crown as the best bird hunter of the night.
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