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> Others of his species in this mixed flock were in varying states of
molt and age, yet only this one bird showed any pink coloration. It's
pure speculation to be sure, but it seems there has to be some genetic
or hormonal reason for these pinkish gulls and terns to show up among
their less colorful brethren. If, as seems to happen, they only sport
this color variation during breeding season, then that certainly lends
credence to the
hormonal theory...

Studies have shown that pigment deposition in feathers can be affected
by sex, age, genes, physiologic condition (including parasite load),
timing of molt (which is under hormonal control), and--in the case of
the carotenoid pigments, of which pink is a representation--diet.  In
fact, the only source of carotenoid pigments in animals is dietary.
Crustaceans are a likely source.  It may be that this gull had a
peculiarly high (for the species) dietary intake of crustaceans before
and during its pre-alternate molt period.  It may also be
extraordinarily vigorous or a bit of a mutant.  But my money is on the
first scenario.  Your question about mating success, of course, assumes
it is a male, which seems likely though not assured.

For some really pink gulls, check out these Ross's (unlike some of the
examples from Florida, pink is a typical breeding plumage coloration
for all birds of both sexes):

http://www.valdosta.edu/~bergstrm/rossgull.html

Brad

--------------------------------------
Brad Bergstrom, Ph.D., Professor
Dept. of Biology, Valdosta St. Univ.
Valdosta, GA 31698-0015
TEL  229-333-5770 /-5759
FAX  229-245-6585  Home: 229-333-0743
e-mail: [log in to unmask]
Web- http://www.valdosta.edu/~bergstrm

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