Fairly common in Gulfstream and warm tropical water. Unusual in cold water. A small black- or brown-and-white shearwater that is often seen sitting and diving with wings open. Loves lines of sargassum (Gulf weed). Fast wingbeats with fairly long glides. Doesn't arc as high or as steeply as MASH. ID: Slim build with proportionally long tail. Black undertail coverts noticeable with care. Capped appearance, usually with straight line through eye, often with white smudge above it. Upperparts vary from shiny black in fresh plumage to paler brown when worn. Can be mistaken for Pterodroma petrels on pelagic trips.