Saturday, July 21, 2012

Heermann's Gull

Heermann's Gulls are atypical gulls--all dark, like in the immature above, or only white-headed, as in the adult below. Both photos where taken in California, the immature bird at La Jolla in March 2012, the adult at Morro Bay in June several years ago. Heermann's Gulls breed off both coasts of Baja California. Non-breeders are regularly found north to San Francisco, with many records north to Vancouver Island. Over 90% of the total population breed on one island, Isla Raza, in the Gulf of California. After breeding from March through July, they move north, joining non-breeders in southern California at the end of May. This "reverse" migration culminates in British Columbia during July and August. Non-breeders may not leave the United States, but breeding birds head south during the fall and winter. With protection from the Mexican government, Heermann's Gull populations are on the rise--perhaps 10-fold since 1975--and now the species tries to breed in California and is occasionally seen further from its normal range (Islam 2002).

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