Sprite – Great Horned Owl

Sprite is a male Great Horned Owl (Bubo virginianus) who came to the WSU Veterinary Teaching Hospital in the winter of 2007. He has a fractured right wing and cannot fly properly. We are unsure what caused his injury, but nevertheless, he is non-releasable. It is also likely that Sprite suffered some neurological damage, as his behavior does not resemble a normal great horned owl. However, the extent of this damage is almost impossible to test.

Great horned owls are one of the most widespread of our owls, occurring throughout North America and in parts of South America. They utilize a variety of habitats, and have adapted well to living around humans. They seem to prefer open woodlands and agricultural land, but can be found in urban, suburban, desert, and boreal areas. They can survive in cold climates due to their thick layer of feathers and the feathering all the way down their toes.

Sprite

They will not build their own nest, but will use an old one from other raptors or large birds, or even steal one that is already being used. Males and females can be differentiated by their calls during mating season; the males have a 3-5 note call while the female’s call contains 5-7 notes and is higher pitched. Great horned owls usually mate in early February (Valentine’s Day anyone?) and are very aggressive protectors of their nests and nestlings.

Over 250 different birds and animals have been identified as prey to these owls, including skunks, snakes, owls and other birds, rodents, and fish. Great horned owls have very powerful feet and can exert 400 pounds of pressure per square inch! That’s 4 times the strength of the adult human jaw! We often say that a great horned owl can snap a broom stick with its feet as easily as a person can snap a crayon with their hands. This power combined with the aggressive nature of the great horned owl allows them to hunt almost anything. They can even hunt porcupines by grabbing them by the head and flipping them on their back. They also have a very limited sense of smell, making skunks a defenseless meal. However, the majority of their diet will consist of common, “easy” prey such as rabbits. They are mostly seen hunting at night, but may also be active around dawn and dusk.

From owlpages.com: “Mammalian prey includes all coexisting rodents, squirrels, mink, skunks, raccoons, armadillos, porcupines, shrews, moles, muskrats, and bats. They may sometimes take small domestic dogs and cats. Bird prey includes all other Owls (except Snowy Owl), grouse, woodpeckers, crows, turkeys, pigeons, Red-tailed Hawks, bitterns, Great Blue Heron, ducks, swans, gulls, etc. Reptiles include snakes, turtles, lizards, and young alligators. Amphibians include frogs, toads, and salamanders. Other foods include fish, large insects, scorpions, centipedes, crayfish, worms, spiders, and road killed animals.”

Great horned owls are well known for being the main predator for many other raptor species. Other owls, red-tailed hawks, osprey, and peregrine falcons have been especially preyed upon by the great horned owl. They also commonly prey on crow nestlings, and are thus often mobbed by large groups of adult American crows.

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.

Sprite’s profile.

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.

Owls also have unique feet relative to most other raptors. Instead of standing with three toes in front and one toe pointing backward (known as the anisodactyl arrangement), they stand with two toes forward, and two pointing backward (known as a zygodactyl arrangement). However, while hunting, owls have the ability to rotate their third toe forward into an anisodactyl arrangement.

Closeup of Sprite’s feet and claws.

Great horned owls are named for the feathers on the top of their heads which resemble horns at a distance. These feathers are thought to be used for communication and camouflage purposes. They have large bodies with brown and black feathering. They are identifiable by their prominent white bib on the upper chest, and their large, yellow eyes. Their facial disks are not as round as in other owl species and are a tan or buff color. This is because they do not rely as much on sound, as on their excellent vision. Great horned owls are one of the largest and most powerful owls in North America, weighing up to 4 pounds. They can take prey up to 2 – 3 times their own weight.

Wild great horned owls live up to 13 years, but in captivity have lived well over 30 years. Juveniles closely resemble adults, so it is difficult to tell their age unless they are still covered in down feathers.

Categories: Raptors