At 00:46 26/03/98 -0600, you wrote:
>At 05:28 PM 3/25/98, Mark E. Mulhollam wrote:
>I'm a little embarassed to bring an anecdotal observation to this scholarly
>discussion, but I was made aware of the display function of eyes when
>watching my brother's Orange-winged Amazon. It periodically dances (last
>time I saw it, its favorite song was Paul Simon's "Will you be my
>bodyguard") and, along with bobbing and fanning its tail, it does the most
>startling thing with its eyes: suddenly snapping the pupils from the widest
>to the tightest "aperture", which displays the red and yellow iris. Must
>be a modification of some normal display behavior...
>
Birds' eyes can be fascinating.
My trusty "Birds their structure & function" by King and McLelland indicates:
Refractive cells (iridiocytes) form a tapeum lucidum of the iris in several
columbiform [dove] species and are responsible for the rapid changes in the
colour of the iris which can occur in these species when excited.
In contrast to mammals, the sphincter and dilator muscles of the pupil are
again striated [This suggests that they will be under voluntary control]. The
movements of the avian pupil can be very extensive and much faster than
mammals and yet the pupil seems unexpectedly unresponsive to light....
Peter
Dr Peter Woodall email =
Division of Vet Pathology & Anatomy
School of Veterinary Science Phone = +61 7 3365 2300
The University of Queensland Fax = +61 7 3365 1355
Brisbane, Qld, Australia 4072 WWW = http://www.uq.edu.au/~anpwooda
"hamba phezulu" (= "go higher" in isiZulu)
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