![]() In many owls the relative position of the ear opening is asymmetrical, being above a so-called blind cavity on one side of the head and below it on the other. Some owls can locate and capture prey in total darkness, relying on their ability to localize the rustle of a mouse in leaves and to fly to that spot. A movable flap (operculum) on the front margin of the opening may function as a baffle to focus sounds. The feathers covering the ear opening are lacy and permeable to sound. The ears are large and surrounded by a ruff of papery feathers that serves to concentrate the sound. Their pupils, which operate independently, can be greatly reduced, protecting the sensitive retina and providing better daytime vision than that found in people. Contrary to popular opinion, owls are not blind in strong light. Various owls have only rods in the retina, resulting in an absence of colour vision but a great increase in visual acuity and light sensitivity. The vision is binocular, and depth perception is often enhanced by moving the head away from the central plane. Remarkable flexibility of the neck compensates for the fixed position of the eyes an owl can turn its head more than 180° in either direction and can thus look directly backward. Virtually immobile, the eye is rigidly encased. The eyes are elongated forward, and each is encased in a tube made up of joined bony elements. ![]() The head is broad to accommodate the exceptionally large eyes. The outer toe points rearward when perching and is normally directed outward or backward in taking prey, providing the maximum possible toe spread. Each toe is provided with a needle-sharp, curved talon. The legs and toes are of medium length and exceptionally strong for the size of the bird. The wings are long and rounded, the tail short.
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