Gwendolyn
Gwendolyn, or Gwen, is a female Western Screech owl (Megascops
kennicottii). She came into the WSU Veterinary Teaching Hospital in June
2004 with extensive injuries to her eyes. She was most likely hit head-on by a
car. The damage to her eyes caused blindness in the left one and severely
limited vision in the right, making it impossible for her to live on her own in
the wild.
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.
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.
