Great Horned Owl
Bubo Virginianus
Order: Strigiformes
Family: Strigidae

Genus: Bubo

The great horned owl may be the most efficient predator that has ever lived. Its approach to hunting is based on a combination of stealth, remarkable powers of prey detection and location, and the application of strength all out of proportion to its size. Victims of a Great Horned Owl’s silent aerial attack typically are not aware of the owl’s presence until they are within the vice-like grip of the owl's talons.

A great horned owl weighs between two to four pounds, has a wing span of 36 to 60 inches, and stands from 18 inches to 2 feet tall. As with all raptor species, the female is the larger of the two sexes.

The visual acuity of these nocturnal hunters is much greater than our own. As with people, the forward position of the eyes provides excellent binocular vision, but their eyes are so large, that our eyes, were they of comparable proportion to our bodies, would be the sizes of grapefruits. The need for superior night vision requires large pupils, whose apertures react to light sources independently of each other. The eyes are plug-shaped, and are fixed snugly into the eye sockets in the skull. As a result, owls cannot "roll their eyes" as we can, or look peripherally without moving their head. Raptors have 14 neck vertebrae, twice as many as we have, and the owl directs its vision by rotating the head 270 degrees, through its lateral and medial axis. Owls have many more motion-detecting rods on their retinas than we do, and the rods are distributed all over the retina, while ours tend to be on the periphery of the fovea, meaning owls are much better able to detect motion than we are. On the other hand, owls have fewer cones on their retina, so they can not resolve color as well as we can.

The great horned owl's “ear tufts” are not ears at all, but feathers which aid in camouflage, and may also indicate their mood. Owls can hear noises ten times fainter than our hearing permits, enabling them to locate prey they cannot see, for example, prey scurrying through the tunnels they excavate under snow pack or prey obscured by brush. The owl's asymmetrical ears are hidden under the dark edges of the facial disk, which is split by the beak and the forehead. The facial dish directs sound to the ears, and the right ear is positioned higher under the disk than the left ear, causing sounds to reach one ear a fraction of a second before it reaches the other. The owl tilts and turns its head until the sounds equalize, and because the owl cannot change the direction of its eyes without rotating the head, the owl is at that moment, staring directly at the location of its prey.


Think of the large Adirondack birds you've seen, for example, wild turkey, grouse especially, or any type of water fowl. Among the features they have in common, is how much noise their wings make while in flight.  Owls are not fast fliers, with a top speed of about 40 mph. However, like virtually all owls, the great horned’s flight is silent due to soft feathers on the edges of its wings.  Other birds preen the ends of the wings to hook the ends of the feathers together so they can fly efficiently.  Owls do not.  What they lose in speed as a result, they make up in stealth, because their flight is totally silent. As the owl drops from its perch and glides towards the sound, silent flight also enables the continuous audible triangulation of the prey's location as the owl closes in.
 
Great horned owls have thick legs and heavy talons. Like our thumbs, the outside talon is opposable, which allows an owl to switch between a perching posture, with three toes in front and one in the rear, and a hunting and grasping posture, with two toes in front and two in the rear, allowing the owl to frame a mammal's spine with its talons as it strikes. The crushing power in a Great Horned’s talons is reputed to be an incredible 500 lbs. per square inch, ten times stronger than the grip of a human hand, so once the talons sink through the prey’s back, most prey are killed instantly. When you hear a biologist joking, that when his time is up, he wants to be taken by an owl, he's saying that the prey of a great horned owl literally do not know what hits them. The great horned owl is the "Jack the Ripper" of the animal kingdom, waiting in silence to deliver an overpowering attack.


Raptors have no teeth, so smaller prey are swallowed whole, while larger prey are torn into manageable chunks, using the beak and talons. The forward talon has a serrated edge, so that the owl can tear lage prey by sinking its talons, reaching down with the beak, and lifting its head up and back. Since feeding on the ground may expose the owl to possible ambush, the great horned owl, the only raptor which can fly while carrying prey equal to its own weight, will attempt to fly its prey to a secure perch on which to safely swallow it. Horny pads under the owls toes allow the owl to control struggling prey as the owl flies.

The great horned owls eat everything from skunks—raptors have a very limited sense of smell—to housecats, whose disappearance is blamed more often than is deserved, on our Adirondack coyotes. Muskrats are a favorite, as are rabbits, squirrels, weasels, minks, martins, bats and anything else they can catch.  They are a main predator of the crow, and take other birds including hawks and smaller owls. Although it is only the size of a redtailed hawk, great horned owls are extremely aggressive, and have been known to drive even bald eagles from their nests.

Owls lack a crop, the throat pouch where other birds store food prior to digestion. Food goes down the esophagus to the proventriculus, a stomach-like organ, where enzymes, acids and mucus begin to break the food down. Next stop is the gizzard, or ventriculous, which separates out the indigestible parts, like bones, teeth and fur, which will be regurgitated later as grayish-white, sausage-shaped pellets or "castings", within about 24 hours of feeding. The act of casting signals that the bird is ready to feed again. Like reptiles and amphibians, birds have only a single intesinal waste vent, the cloaca, from which they expunge a fecally acidic white paste and a clear urinary fluid. The reproductive organs are also concealed within the cloaca, which is why, aside from the fact that females are considerably larger, you can not tell a raptor's sex without a blood test. Owls often perch on pine branches high above and along the Wildlife Refuge trail, so look for the tell-tale castings under the trees, or the whitewash fecal spray on the trunks and branches.

There is something comically humourless about owls, in the sense that I've never seen an owl do anything that appeared to be playful, or fullfilling any need for amusement. While we often see red tails chasing each other and diving as a part of courtship, owls appear stiff and serious, always businesslike. Even their courtship is almost formal, with the bowing and presenting of food.

Utah, the male, was struck by a car in Utah, and Artemis, the female, became tangled in barbed wire shortly after first leaving the nest in North Carolina. Poodle, an orphaned fledling, was released in September.