Not wishing to miss a chance to remind birders what a great resource the California Bird Records Committee web site is -- and the "Rare Birds of California" book that it complements....
The Humboldt County (Orick vic.) report from 30 Dec 2006 was not accepted by the CBRC;
There is an additional non-accepted record from Upper Newport Bay in August 1977 (see Rare Birds of California).
The Salton Sea bird from 1 May (photos of which are diagnostic for Great Black-backed in my opinion, but the record of course awaits CBRC review) would indeed be a first for California if accepted.
Kimball L. Garrett
Ornithology Collections Manager
Natural History Museum of Los Angeles County
900 Exposition Blvd.
Los Angeles, CA 90007 USA
] On Behalf Of Ken Burton
Sent: Friday, May 03, 2013 3:12 PM
Subject: [CALBIRDS] Re: FW: NESS Great Black-backed Gull
I believe there is an accepted GBBG record from Humboldt County.