Breeds in Gulf of California (particularly Isla Rasa) south to Nayarit; also Baja California (from San Benito Is off Pacific coast) and northern very sparsely in southern California, occasionally and irregularly to San Francisco Bay.
 
Population
Estimated population is 530,000 (2010) and fluctuating.
Heermann's Gull (Larus heermanni) [XC159223]
by Ian Cruickshank from Rocky Point Bird Observatory, Metchosin, Vancouver Island, BC, Canada (call, calls, long calls)
Heermann's Gull (Larus heermanni) [XC66178]
by Ian Cruickshank from Rocky Point Bird Observatory, Vancouver Island, BC, Canada (call)