Small black-and-white shearwater with relatively long tail and somewhat rounded wings. Usually flies low to the water with fluttering wingbeats, but in strong winds it can fly with high wheeling arcs. Undertail coverts are typically dark, but this can be very difficult to see in the field. Compare with Manx Shearwater, which is larger with longer, more pointed wings, light undertail coverts, and a darker face. Found over warm tropical waters, especially around floating mats of Sargassum weed. Often seen singly or in pairs but can gather in loose flocks, sometimes loafing with other shearwater species.