Blue (Phalacrocorax penicillatus)

In breeding season it's a good deal easier to tell the various California coast cormorants apart, thanks to their distinctive white patches and plumes. When those aren't visible, you have to rely on size (hard to judge at a distance and when they're not side by side), location (but those overlap), and the colors of their lores (but those are also brighter and easier to see in breeding season). This one, with his bright blue throat pouch, is obviously a Brandt's.