College of Veterinary Medicine |

Healthy Animals, Healthy People, Healthy Planet


Sully is a male Western Screech Owl (Megascops kennicottii) who came to the WSU Veterinary Teaching Hospital in September of 2009. He had an injury to his right wing, most likely caused by a collision with a car. The wing was dislocated at the shoulder, effectively permanently immobilizing it. Since Sully no longer has the use of that wing, he is unable to fly and is not releasable.
There are 3 types of screech owl 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 much darker bill color. The Whiskered screech owl is smaller than the other two and has an orange tinge to its eye color (the others have yellow eyes). The screech owls have color patterns that allow them to blend in perfectly with the trees in their environment. They also all have “ear tufts” on the top of their head (like the Great Horned Owl) which have nothing to do with ears, but are actually just longer feathers that can be raised or lowered. Contrary to their names, screech owls don’t screech. Instead they have a trilling "hoo-hoo-hoo" that often starts out slower then speeds up – kind of like a bouncing ball. Sully is one of the most vocal birds in the club, and greets everyone with a demanding "Whooo!?".
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 or nesting boxes. 
Screech owls are (primarily) nocturnal and hunt mostly 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 asymmetrically placed ears (the left is more up and forward and the right is down and back). This adaptation allows owls to locate prey by triangulating the source of a sound. Some owls rely more on sound than others. The screech owl has very large eyes in proportion to its facial disk. This tells you that they actually depend more on their vision for locating prey (although hearing is still important).  Owls with a larger, more defined facial disk would likely depend more on their hearing (for example, the barn owl).
All owls have several characteristics that make them unique among raptors. For example, the front edge of their flight feathers is serrated like a bread knife. This breaks up air turbulence and allows them to fly 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 beyond! 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 way up to stand taller. 
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