Compared to a human's eye, bird's eyes are much larger. The biggest
part lies within the skull, only a small area can be seen. If one has
a closer look to a budgie's eye, one can easily recognize the
pupils (5a) and an
iris ring (5b). Depending on the bird's colour
variety, the pupil is black, dark-brown or red. The iris ring
can be white or black. In the latter case it seems as if the bird has
no iris ring.
Humans and most mammals have two lids which can be opened and closed from above downwards. In addition to their upper eyelid (5c) and lower eyelid (5d), birds have a third, inner lid, the so called nictitating membrane (5e), see below. On the edges of the upper and lower eyelid some tiny hairs can be found. They are roughly comparable to the human lashes and can only be seen from very close.
The nictitating membrane (5e) opens and closes
vertically and is transparent. It is very hard to see in general.
Link tip: Do you want to discuss with experts and other bird owners about your bird's health? Then please feel free to visit the English forum of 
. Of course you will meet me there, too. My nickname is "Feenseeschwalbe".
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