No they're not. They are double-crested cormorants and they are native to California. They are protected under the federal migratory Bird protection act. When they become a nuisance a depredation permit can be applied for, with the feds (USFWS). Sometimes they are granted, like when a lake manager can show a monetary loss for all the stocked fish he is losing to them.
Thank you for following up with clarity. Last time out to a local lake I did see what appeared to be both Mexican and double crested birds and I thought to myself I should follow up here, but things just got busy. No breeding plumage on the double crested type, though, so I'm still not so sure.
Whichever they are, they are a nuisance for anglers for sure.
I see SARL firing bottle rockets at them when they get aggressive on stocking day. They should be taking them out with mortars or AA guns...I've personally seen at least 5 trout 21-2 lbs each, fresh, on thursday afternoons and friday mornings flopping in the dirt 100-200 yards south of the river, well outside the fenceline. The fish drop them as they fly back to their nests. I work on the freeway widening project, that's how I find them.