College of Veterinary Medicine |
Kotori

Healthy Animals, Healthy People, Healthy Planet
Kotori the Western Screech Owl

Kotori is a male Western Screech Owl (Megascops kennicottii) who came to the WSU Veterinary Teaching Hospital in 2014. He was found as a owlet on the ground and was brought in. It was believed that once he was older he could be released back into the wild. However when they tested his flight abilities they discovered he could not fly due to his flight feathers growing in and twisting. This twisting makes it so he can not get the lift required to fly. This makes Kotori unreleasable.

There are 3 types of screech owls in the United States: the Western Screech Owl – found West of the Rocky Mountains, the Eastern Screech Owl (Megascops asio) – found East of the Rocky Mountains, and the Whiskered Screech Owl (Megascops trichopsis) – found in the Southwestern states and Mexico. The Eastern Screech Owl is similar in color and size to the Western, but the Western has a darker bill color. The Whiskered Screech Owl has an orange tint to its eye color, rather than the yellow of the Western and Eastern Screech Owls. The screech owls’ color pattern ranges from a mottled grey and white to an orangey brown color. Their feather pattern allows them to blend in perfectly with the trees in their environment. They also all have “ear tufts” on the top of their head, which have nothing to do with their ears, but are actually just longer feathers that can be raised or lowered. There is some debate over what exactly owls use their ear tufts for, but some believe that they are used for expression or display purposes, while others believe that they are used to break up the owls’ outline and provide better camouflage. Contrary to their names, screech owls don’t screech. Instead they make a trilling "hoo-hoo-hoo" sound.

Western Screech Owls live in riparian zones (the green, vegetated areas on each side of streams and rivers) or urban/suburban areas with mixed coniferous and deciduous trees. They are cavity nesters; nesting in tree hollows, nesting boxes, or cavities made by other animals. They are secondary nesters and will not make their own cavity.

Screech owls are crepuscular which means you will most commonly see them hunting during dawn and dusk. They mostly prey on small rodents like mice. However, they are opportunistic and will also hunt amphibians, reptiles, small fish, insects, bats and small birds. Like all owls, they have a facial disk consisting of stiff feathers around the beak and eyes that direct sound back to their ears. However, screech owls have a relatively small facial disk compared to their eye size. This is a clue that they rely more on sight rather than hearing to hunt. Owls with facial discs that are large compared to their eyes rely more heavily on hearing to hunt (for example, the Barn Owl relies mainly on its hearing). If a Western Screech Owl was put in a darkened stadium with a single mouse, it would need at least a candle’s worth of light to be able to hunt the mouse in that stadium (but only one candle would be sufficient for it to find the mouse anywhere in the entire stadium!).

All owls have several characteristics that make them unique among raptors. One is the asymmetrical placement of their ears. Owls’ ears are simply holes on the sides of their skull that are covered by feathers. The right ear is up and forward while the left ear is down and back. This adaptation allows owls to locate prey by creating a sound triangle (triangulating) and pinpointing exactly where the sound is coming from. This helps while hunting in very low light.

Another unique owl characteristic is that the front edges of their primary flight feathers are serrated like a bread knife. This breaks up air turbulence and allows them to fly almost completely silently. There are two purposes for this – for one, owls do not want their prey to hear them coming. The second reason is that owls depend so much on their hearing that any noise from their wings would hinder their hunting ability.

Another characteristic of owls is the large size of their eyes. They are so large, in fact, that there is no space for extrinsic muscles to move the eyes. As a result, there is a bony ring around each eye that fixes them in place. While humans and most mammals can look to the left and right with their eyes without turning the head, owls cannot. To compensate for the lack of eye movement, owls have twice as many vertebrae in their neck as mammals – we have 7, they have 14. This allows them to turn their head completely backwards and then over the opposite shoulder. While they cannot rotate their head 360 degrees in each direction as many people believe, they can rotate it about 270 degrees each way. Because of the large number of vertebrae, owls can also extend their neck up to look taller and thus more imposing to any predators.

Owls also have unique feet relative to most other raptors. Instead of standing with three toes in front and one toe pointing backwards (known as the anisodactyl arrangement), they stand with two toes forward, and two pointing backwards (known as a zygodactyl arrangement). However, while hunting, owls have the ability to rotate their third toe forward into an anisodactyl arrangement. Unlike other raptors, owls have no crop for food storage. They often swallow their food whole or in large chunks, and it goes directly to the stomach. In the stomach, a pellet (or cast) is formed from fur, bones, and other indigestible material. The pellet is then regurgitated 10 or more hours later. Larger owl pellets can be easily dissected to find the bones of their most recent prey.

Washington State University