Why is the position of the eyes of a macaw makes it difficult to judge distance

The position of the eyes of a Macaw are as follows. Each eye is located on either side of the birds head. This is called Monocular vision, opposed to our eyes which are located in front of our head, adjacent to each other. Mono comes from the Greek root word meaning 'alone'. Making it understandable that, that type of vision is more limited.  The operation of their eyes, view things differently in comparison to that of binocular vision (what we humans have). They have a more broad view but cannot judge distance or depth very well.
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