Owls are easy to recognize. They have an almost human appearance, with upright posture, large rounded heads, and large eyes that face forward (most birds have eyes on the sides of their heads). All owls are carnivores, or meat-eaters, and several adaptations make them effective hunters, including a hooked beak for tearing flesh and strong feet tipped with sharp talons, or claws. The toes can be used in a two-forward, two-backward arrangement for a good grip on prey (most birds have three toes pointing forward and one pointing backward). Feathers are unusually soft, allowing for silent flight, so owls can hear their prey and approach it without warning.
Most owls are nocturnal, active at night and asleep by day. Adaptations for night hunting include eyes that can see in low-light conditions and very sensitive hearing. The eyes are enclosed in a ring of bone and cannot move freely, so owls must turn the entire head to look sideways. They do have extra flexible necks that allow the head to turn 270°, so an owl can see what's behind its back. Many owls have ears positioned asymmetrically on the head, with one higher than the other. This arrangement helps owls locate the source of a sound. Feathers on the face are arranged in a flat circle called a facial disk. It works much like a satellite dish, focusing sound waves on the ear openings.
Most owls have subdued, or dull, color. The feathers are usually gray or brown with spotted or streaky patterns that create a camouflage effect, allowing the owl to blend in with its surroundings. This is useful when owls are sleeping during the day. The owls avoid being noticed by predators such as hawks. Male and female owls usually look alike but females are often are slightly larger.
The heaviest owl is the Eurasian eagle-owl, which weighs
9.25 pounds (4.2 kilograms). At 28 inches (71 centimeters), however, it is a little shorter in length than the great gray owl, which measures 33 inches (84 centimeters) long. The smallest owl is the elf owl, which weighs 1.4 ounces (40 grams) and is about 5 inches (13 centimeters) long.