Ring-billed Gull (leucistic)

Discussion of albinism/ leucism in birds:

http://www.birds.cornell.edu/pfw/AboutBirdsandFeeding/Albinism_Leucism…

"Typically birds with abnormally white feathers do not survive long because they are so much more visible to predators. Those that do survive may have trouble attracting a mate. Consequently, the mutated genes that cause albinism and leucism are less likely to be passed on to a new generation."