Fw: Kookaburra eyes

To: "" <>
Subject: Fw: Kookaburra eyes
From: brian fleming <>
Date: Wed, 24 Feb 2016 06:03:47 +0000
Dear Bill,
    This is a splendid pair of photos, good enough for any text-book,
showing the third eyelid or nictitating membrane.  This is present in
all birds and some mammals (not humans, though we have a vestige in the
inner corner of the eye). This membrane covers the eye as a protection
in situations where injury is possible - such as dealing with prey or
when feeding young.  It probably also cleans the cornea.  I don't know
if it covers the eye under-water in diving birds.  I am sure the bird
can see through it.

   Some people discard photos where it shows, because the eye doesn't
'look right'. But it is a normal function and not a deformity.

Anthea Fleming

On 24/02/2016 3:08 PM, Bill Stent wrote:
> I was wandering around Banyule Swamp this morning when I found a
> Kookaburra.
> Taking some photos I noticed that when the bird's head was turned at a
> particular angle the eyes looked clouded, but on a different angle they
> appeared clear (see attached photos).
> Does anyone know what this is?  Is it an optical thing, related to the
> efficiency of the eyes, or something else?
> Bill
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