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my, what big eyes you have.... — Fotopedia
Close up action; Barking Owl
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Barking Owl

The Barking Owl (Ninox connivens), also known as the Barking Boobook or Winking Owl, is a nocturnal bird species native to mainland Australia and parts of Papua New Guinea and the Moluccas. They are a medium-sized brown owl and have an extremely characteristic voice that can range from a barking dog noise to a shrill woman-like scream of great intensity. Barking owls are often said to be the source to the myths and legends surrounding the Bunyip.


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Owl

Owls, birds of the order Strigiformes, include about 200 species of mostly solitary and nocturnal birds of prey typified by an upright stance, a large, broad head, binocular vision and binaural hearing, and feathers adapted for silent flight. Exceptions include the diurnal Northern Hawk Owl and the gregarious Burrowing Owl.

Owls hunt mostly small mammals, insects, and other birds, although a few species specialize in hunting fish. They are found in all regions of the Earth except Antarctica and some remote islands.

Owls are divided into two families: the true owls, Strigidae; and the barn-owls, Tytonidae.


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Binocular vision

Binocular vision is vision in which both eyes are used together. The word binocular comes from two Latin roots, bini for double, and oculus for eye. Having two eyes confers at least four advantages over having one. First, it gives a creature a spare eye in case one is damaged. Second, it gives a wider field of view. For example, humans have a maximum horizontal field of view of approximately 190 degrees with two eyes, approximately 120 degrees of which makes up the binocular field of view (seen by both eyes) flanked by two uniocular fields (seen by only one eye) of approximately 40 degrees. Third, it gives binocular summation in which the ability to detect faint objects is enhanced. Fourth, it can give stereopsis in which binocular disparity (or parallax) provided by the two eyes' different positions on the head give precise depth perception. Other phenomena of binocular vision include utrocular discrimination, eye dominance, allelotropia, and binocular rivalry. Binocular vision, also, helps with performance skills such as catching, grasping, and locomotion. Orthoptists are eyecare professionals who fix binocular vision problems.


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Eye

Eyes are the organs of vision. They detect light and convert it into electro-chemical impulses in neurons. The simplest photoreceptor cells in conscious vision connect light to movement. In higher organisms the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, and transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs, chordates and arthropods.

The simplest "eyes", such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, which is sufficient for the entrainment of circadian rhythms.[citation needed] From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment.