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Summary: Senses and Vocalisations
Valentin Amrhein
Birds are extremely visual animals. Songbirds and raptors can resolve
details at 3 times the distance that humans can. The eyes of eagles and
owls are as big as human eyes. The eye of an ostrich is the largest of any
land vertebrate.
Because birds' eyes are generally set on the sides of their heads,
binocular vision is atypical. Many birds examine nearby objects with one
eye at a time.
1
In birds, both the cornea and the lens change their curvature while
focusing: only the lens does so in mammals. In the retina, raptors can
have 1 million colour receptors per square millimetre (humans: 200'000).
Unlike the mammalian retina, the avian retina has no embedded blood
vessels. Instead, the vascular supply system ins concentrated in the
pecten.
Fast-flying birds have temporal as well as well as central foveae (Sehgruben).
2
Due to the complex retinal structure, birds can detect both rapidly
moving and slowly moving objects. Birds can resolve movements faster
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