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Larus livens
Since it was spotted @ Canarias and not in the California Gulf in Mexico, I think this is one of 2 species:
Larus fuscus http://en.wikipedia.org/wiki/Lesser_Blac......
or
Larus michahellis http://en.wikipedia.org/wiki/Yellow-legg......
And watching at the wings color I think is most likely to be the second one (Yellow-legged Gull aka Larus michahellis)