Found on every continent except Antarctica, owls have been part of human culture and mythology for millennia. They're viewed as everything from wise old good luck charms to demonic harbingers of death. Why such symbolism? Part of that fascination comes down to an odd anatomy, one that makes them stand out among other bird species.
Many species are nocturnal, they're nearly silent fliers, they can swivel their heads around, they are often more easily heard than seen thanks to exceptional camouflage, and they certainly have expressive faces. All of this adds up to a very strange bird. Here are a few ways owls are weird, but wonderfully so.
Not exactly eyeballs
Owls don't have eyeballs. Rather, they're more like eye tubes. They're elongated and held in place by "sclerotic rings," a bony structure in the skull. Because of this, owls can't really move or roll their eyes. That's why they have heightened mobility in their necks, but we'll get to that later.
Because the eyes are forward-facing, owls have binocular vision similar to humans, meaning they can see an object with both eyes at the same time. This gives owls a great ability to judge height, weight and distance. However while humans have a 180-degree field of view with about 140 degrees of it being binocular, owls only have a 110-degree field of view with about 70 degrees of binocular vision. But what they lack in binocular vision they make up for in extraordinary night vision and far-sightedness.
However, because they are far-sighted, they can't see objects up close. When they catch prey, they use filoplumes — small hair-like feathers on their beaks and feet — to feel out their food.
Finally, owls have not one, not two, but three eyelids: one is for blinking, one is for sleeping, and one is for keeping those precious peepers clean.
Okay so let's clear one thing up right away. Owls can't turn their necks 360 degrees. It looks like they can, but it's actually only (only?!) 135 degrees in either direction from facing forward. This gives them an amazing total of 270 degrees of movement.
It's not easy to turn your head all the way to see over your shoulders, so owls have some special adaptations. First, instead of seven vertebrae in their necks like the average bird, owls have double that number! But their adaptations go well beyond that. They have extra upgrades that help them survive while they turn their heads so dramatically and quickly. They have alternative blood vessels routing blood to the head, blood pooling systems to keep blood circulating to and from the brain when their neck movement cuts off circulation, and air-cushioned vessel casings so they don't rupture a blood vessel when snapping their neck around 135 degrees to look over their left shoulder.
Owls have amazing eyes, sure. But often it's their ears that do the real work in hunting. Many species of owls have ears that are not only placed asymmetrically on their head but are also different sizes. The two differently sized and placed ears receive sound at slightly different times, providing the birds with an exceptional ability to pinpoint the location of sound; when a sound is equally loud in both ears, the owl knows it has zeroed in on the source and distance.
Meanwhile, their flattened faces funnel sound to the ears, magnifying it so that they can detect even the slightest sound from tiny prey.
Owls are the ninjas of the bird world. (Photo: zpics [CC BY-ND 2.0]/Flickr)
Owls are known as silent fliers. They need to be completely quiet if they want to swoop in on fast-moving prey. To accomplish this, they have broad wings that allow them to glide and minimize flapping, which is what creates most of the noise from a flying bird. Also, many species of owls have special flight feathers that minimize sound when flapping their wings.
Along the leading edges of the primary flight feathers are stiff fringes, reminiscent of the teeth of a comb, that act to reduce turbulence. Then on the trailing edges of the same feathers are soft fringes, sort of like the frayed edges of a torn piece of cloth, which further reduces remaining turbulence. The wings are also covered in downy feathers to dampen sound even more.
With these specially designed feathers, instead of the woosh-woosh-woosh sound we hear from the wing beats of large birds like ravens, it's difficult to hear owls at all. This gives them the ability to sneak up on unsuspecting prey.
An owl's feet are special, too. (Photo: Chris Gladis [CC BY-ND 2.0]/Flickr)
Owls have a foot structure called zygodactyl, which is similar to the structure of the feet of woodpeckers and parrots. Owls have four toes, three of which face forward and one backward when flying. However, when perched or grasping prey, the outer front toe can swivel back so that two toes face forward and two face backward. This allows an owl a better grip on prey or a branch.
But for a truly exceptional grip, owls have the ability to lock their toes around an object so that they don't need to continually contract their muscles. Maximum grip with minimal effort.