Paul <tuisto at oz.net> said;

"Symmetrical placement is almost surely a pattern mutation. Deb's
robin is not typical for a spotting (pied) mutation and injury seems as
reasonable a cause as any. Kelly's robin, on the other hand seems like it
could be a spotting mutation even though it had blotches on the back. The
white primaries are appropriately distant from the spinal cord. The "mostly
white" head probably also includes ventral areas, and it is hard to imagine
that a robin could sustain serious injury to most of its head and survive
without an excellent insurance plan."

well, symmetrical placement of depigmented areas are not necessarily
a pattern mutation, cuz (harking back to avicultural observations --
sorry, i don't mean to ruffle anyone's feathers) i have seen many
"pied" parrots (and a few species of passerines that are "pied") with
asymmetrical placement of pigment splotches. in fact, the value of
such "pied mutation" birds is directly proportional to the symmetry
of pigment location.

of course, i may be splitting feathers when defining "symmetry" of
these pigment splotches. some birds have almost identical markings
on each side (wing, etc.) while others have quite a bit of variation
in the size and shape of splotches. however, these splotches, if i
recall correctly, typically occur in the same *general* areas.

Deborah Wisti-Peterson email:nyneve at u.washington.edu
Department of Zoology, University of Washington, Seattle, Wash, USA
Visit me on the web: http://weber.u.washington.edu/~nyneve/
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