Re: Birds' eyes

[Shane Raidal <>]

At 08:16 AM 3/27/98 +1000, you wrote:
>Steve's comment concerning the opening/closing of iris by Amazon
>parrots might be relevant here...both would seem to be some sort of
>display.

The regular fast opening and closing of the iris is called "hippus" and the
best example of this in Aus birds that I can recall is the rainbow lorikeet
but most lorikeets and other psittacine birds display hippus.  Unlike
mammals the avian iris contains striated muscle which means they have more
"control" over the pupil diameter.  They can probably alter the pupil much
in the same way we wink.  

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Shane Raidal  BVSc PhD MACVSc 
Lecturer in Veterinary Pathology
Veterinary and Biomedical Sciences
Murdoch University               phone:  +61  8  9360 2418
Perth,WA, 6150                           fax:  +61  8  9310 4144  
Australia                           
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