This is a rare but regular winter visitor to California. This is an immature bird showing the distinct pink-based bill with contrasting black tip. Note also the barring on the wing coverts and the white wing tips. It can be difficult to age immature Glaucous Gulls due to variation in molt and appearance.The dark eye and brown mottled mantle suggest that this is a SY (2nd Calendar Year) bird hatched in 2019. Four subspecies usually recognized. By range, this is L. h. barrovianus which breeds coastally from west-central Alaska north and east across northern Yukon to northwest Mackenzie. It winters from southern. Alaska south to the Pacific Northwest, with some reaching south to northern Baja California and northern Sonora. It is a smaller subspecies with adults averaging a slightly darker mantle than L. h. leuceretes of Eastern North America. Some authors merge leuceretes with nominate hyperboreus of Europe. Note short wing-tip projection beyond the tail, less than length of the bill. This can help distinguish them from the similar but much smaller Iceland Gull (L. g. glaucoides). Canon PowerShot SX60.
References:
Burger, J., Gochfeld, M. & Garcia, E.F.J. (2019). Glaucous Gull (Larus hyperboreus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from https://www.hbw.com/node/53979 on 18 March 2019).
Howell, S.N.G. and Dunn, J. (2007) A Reference Guide to the Gulls of the Americas. Peterson Field Guides, New York.
Malling Olsen, K. & Larsson, H. (2003) Gulls of Europe, Asia and North America. Christopher Helm, London.
Weiser, E. and H. G. Gilchrist (2012). Glaucous Gull (Larus hyperboreus), version 2.0. In The Birds of North America (A. F. Poole, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bna.573