This adult Ring-billed Gull has a light
pinkish-orange plumage flush on the breast. Its legs were a
brilliant yellow with touches of orange on the feet. Its bill was
also an intense yellow, similar to the legs, and more vivid than the
other Ring-billed Gulls. Oshawa Harbour on 17 February 2016. .
The article below explains that a
carotenoid pigment called astaxanthin may be responsible for the
pinkish plumage flush on the breasts of some gulls. Its presence in
the plumage of gulls may be related to diet. Only a few Ring-billed
Gulls exhibited this pigment, primarily those on the West Coast,
where they eat a lot of salmon. Ring-billed Gulls with this pinkish
plumage flush apparently increased after about 1998 when fish
hatcheries added astaxanthin to the diets of juvenile salmon.
Another explanation for the pink flush is environmental or
physiological. The article does not discuss the coloration of bare
parts, which in gulls intensifies with the onset of breeding
plumage. In the above gull, it is brilliant, and this together with
the pink plumage flush may be very attractive to a prospective mate.