In the last Note we admired the Green Heron's remarkable neck. Its eyes direct that hunting prowess. They're positioned forward and are angled down past the tip of its beak toward prospects for a meal.
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Green Heron and Black Duck |
That eye configuration is not universally advantageous, however. In the very same environment ducks depend on an entirely different ocular arrangement.
The duck's filter-feeding strategy does not rely on binocular vision to guide its bill. Dabbling goes more by feel than by sight. Its eyes are conveniently located high above foraging and peripherally where they can stay alert for trouble.
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Double-crested Cormorant and Green Heron |
The eyes of a cormorant, like a heron's, are positioned to pursue a fish right into its bill.
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Red-tailed Hawk |
Soaring raptors also optimize binocular vision for locating prey from high in the air, and for judging distances.
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Merlin |
On the other hand this small falcon's eyes are located more laterally. While hunting from a perch or on winged patrols low over the ground, its relatively side-looking cone of vision serves it well.
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Barred Owl |
Owls, with a human-proportioned face, have maximized the advantages of forward eye positioning for their low-light hunting strategy. This highly specialized vision helps them pinpoint prey that they initially locate by sound. They forego some sight capabilities that other birds depend on.
Varied anatomies are crucial to success in particular niches and strategies. There is no single visual ideal.
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