Let's Celebrate Pet Birds!
T.J. Lafeber D.V.M.

Remarkable Eyes, Amazing Vision



Remarkable Eyes, Amazing Vision

The list of unusual and remarkable qualities of a bird includes colorful feathering, song, graceful nature, and flying ability; and yet, one of its most stunning attributes is its eyes. The eyes of a bird have reached the state of perfection superior to that of any other animal. This advanced state allows the bird to visually obtain more information about its surroundings than available to any other living thing. The eye collects data about the direction, distance, size, shape, color, three dimensional depth, and motion of an object. Whether this be an enemy or a food source, the bird has an advantage.

Exceptionally Keen Vision
Children attempting to ''sneak up'' on a bird are amazed that even though the bird is facing the opposite direction, their actions are detected and the bird flies away. The incredible range of vision is due to the placement of the eyes on the sides of the head. This fact, coupled with the shape of the cornea, allows for wide-angle vision.   Birds focus straight forward with both eyes, but also see sideways just as effectively. Their peripheral vision, especially related to a moving object, is also keen.

(Photo of Eye)

Birds' eyes may seem small but proportionately are much larger than ours. Note that the only visible portion of a bird's eye is the cornea. The largest part remains hidden. The eyelashes are small feathers-not hairs.

Birds have their vision fixed on you as soon as you enter the room, and you remain constantly under surveillance until you leave. Not that your bird necessarily mistrusts you, but they do have the ability to see you and everyone else present, even if the room is full of people.

You'll probably never be certain exactly what your bird's eyes are watching because their head does not point to the object under observation. And when your bird tilts his head he's just getting a look at you from another angle.

Predatory birds flying hundreds of feet above a field can detect a mouse with an ability unknown in other animals. With an extraordinary scanning and detection system, they can rapidly analyze the content of their field of vision and dive quickly on their prey. A person would take much longer to visually search the same space.

Skillful flight requires sharp eyesight and quick muscle coordination. An important part of flight is the bird's ability to focus rapidly. To avoid hitting branches when flying through trees and bushes or for catching insects in the air, birds have strong powers of near and far focusing.

Your bird has his ''eye on you" when you are within visual range.

Adaptations For Superior Vision
To perform the functions nature has assigned, a large eye is required. For their size, birds have enormous eyes, although the mass stays hidden in the skull. The eyelids open to expose only that small part of the eye (cornea) needed to allow entrance of light. So while the eye externally appears small, the opposite condition exists.

Birds have three eyelids-an outer, upper and lower lid and the third eyelid just inside the others. The third eyelid (membrance nictatans) performs the job of cleaning and moistening the cornea. The inner surface is covered with cells which possess brushlike processes, so that the cornea is painted with tears at every blink. Like a windshield wiper, it cleans the undersurface of the eyelid on the return journey of each sweep. Pet birds blink with their eyelid 30 - 60 times a minute, and usually so swiftly as to be undetected. A large gland under the third eyelid furnishes much of the lubrication for the eye.

The upper and lower lid protects the eye and closes when the bird is sleeping. If the upper and lower lids are closed in a ''sleepy'' fashion, especially in an active environment, it can be a reliable sign of sickness.

In summary, life as a flying animal demands superior vision.

Watching For Eye Problems
Birds' eyes are exceptionally resistant to some of the problems seen in mammals. Local infections, such as conjunctivitis, are unusual, but when troubles do appear, they are much more serious and difficult.

Because birds always want to present themselves as healthy, they face you with their good eye and hide an abnormal one. Thus, an eye infection may be missed until the owner becomes suspicious.

For any eye problem see your veterinarian.

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