Birds

are furnished with a mouth, but with an exceptional one,
for they have neither lips nor teeth, but a beak. Neither have they
ears nor a nose, but only passages for the sensations connected with
these organs: that for the nostrils in the beak, and that for
hearing in the head. Like all other animals they all have two eyes,
and these are devoid of lashes. The heavy-bodied (or gallinaceous)
birds close the eye by means of the lower lid, and all birds blink
by means of a skin extending over the eye from the inner corner; the
owl and its congeners also close the eye by means of the upper lid.
The same phenomenon is observable in the animals that are protected by
horny scutes, as in the lizard and its congeners;