Brandt's Cormorant

Brandt's cormorant is a sea bird found along the Pacific coast of North America, from the southern coast of Alaska to Baja Sur and the Gulf of California. Those north of Vancouver Island migrate south during the winter. Part of its Latin name, penicillatus, means painter's brush or pencil of hairs, referring to white plumes on its neck and back during early breeding season. 

A rock full of Brandt's cormorants off of Anacapa Island. 

All About Birds provides a much better identification than Wikipedia: Breeding birds are black with a purple sheen on the head and a blue gular pouch (skin patch on the chin). Non-breeding birds are blackish with a paler brown chin patch. Juveniles are brownish overall with a paler neck that forms a "V" shape on the breast (often visible on resting birds) and have a pale chin patch. 

A brownish juvenile on the right.

Breeding birds with blue gular pouch and white plumes on the neck and back. 

In March I took a pelagic bird tour with Island Packers out of Oxnard, California. We visited the eastern end of Santa Cruz Island and pretty much circled Anacapa Island.