Re: robin's eye blue

Unless the bird is blind, I can think of no other explanation. Also, see 
http://en.wikipedia.org/wiki/Nictitating_membrane

Barry
----- Original Message ----- 
From: "Alistair Fraser" <[EMAIL PROTECTED]>
To: <[EMAIL PROTECTED]>
Sent: Monday, June 22, 2009 8:24 AM
Subject: Re: robin's eye blue


> Barry, Len,
>
>
> ***
>
>> No it is not! You caught it as it was 'wiping' its eye.
>> Barry
>>
> ****
>
>> Nice capture of the following Alistair.  I don't know how many shots
>> I have of perfect bird poses only to have this mar the image.
>> "Many animals have a third eyelid called a nictitating membrane. This
>> clear eyelid can be drawn across the eyeball for protection from
>> debris, prey, or the dryness of air, similarly to regular eyelids."
>> Len
>
> ****
>
> Well, I considered the possibility of the picture showing the
> nictitating membrane, but tentatively discarded the idea. Here are my
> reasons:
>
> 1) Some time ago I posted a pair of eagle pictures to the list under
> the title nictitating (below). Since then, every time I have seen it
> with other birds, the membrane has turned the eye cloudy: a diffuse
> white.
>
> 2) The robin's eye shows a strongly pattered blue (see detail, below).
> Plus, there seems to be the edge of a membrane visible on the left
> side of the eye. This suggesting that the nictitating membrane was not
> fully drawn across the eye (assuming it is drawn from the back to the
> front).
>
> So, I wondered: Am I seeing the pattern or structure of the a portion
> of the retina itself?
>
> Ok, have at me.
>
>
> Alistair
>
>
> >
> 


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