Black Storm-Petrel. Off San Diego, California. October 4, 2014. Greg Gillson.
My two pelagic trips from San Diego this fall yielded storm-petrels of several species. Unfortunately, none were close to the boat. The most common species is Black Storm-Petrel. They are larger (for storm-petrels, anyway, at 9 inches long) with long wings that are flapped deeply above and below the horizontal, as depicted in these photos. Their deep, purposeful wing strokes, and overall dark coloration reminds me of Black Terns.