| 1. |
Vision is a diurnal bird of prey's most important sense for hunting and reacting to danger.
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| 2. |
Diurnal birds of prey have excellent vision. |
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The eyes are proportionally larger than the eyes of other vertebrates, providing larger and sharper visual images. |
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The retina has more rods and cones (the eye's sensory cells) and is one-half to two times as thick as the retina of other vertebrates. More sensory cells mean better visual acuity. |
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As in humans, the point of sharpest vision is the fovea. Foveae are funnel-like areas of the retina packed with color-perceiving cone cells. Humans have one fovea per eye, while diurnal birds of prey have two. |
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In addition, many diurnal birds of prey have proportionately more sensory cells in the upper half of the retina. This helps a bird perceive images when looking toward the ground from a perch or when flying. As a consequence, to scan the sky, they must turn their heads upside down. |
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Like humans, diurnal birds of prey focus on objects through binocular vision (using two eyes to see); but, can easily detect movement at the edges of their viewing range using just one eye. |
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| 3. |
Diurnal birds of prey are thought to see objects at a distance about the same as or up to three times better than humans. The wedge-tailed eagle (Aquila audax) can discern objects at a distance twice as far as humans. On the other hand, an American kestrel has visual acuity equal to a human's (Martin, 1987). |
| 4. |
Diurnal birds of prey see color, which may play an important role in food identification and reproductive behavior. |
