Small fluttery seabird, abundant in the Atlantic but rare in Pacific Ocean. Can sometimes be seen from land, but mostly stays offshore. Dark blackish-brown overall with white rump patch and pale wing panels; usually conspicuous. Long legs extend past the tail in flight; difficult to spot unless close. Wingbeats are lighter and shallower than other storm-petrels. Patters feet on surface of water when feeding more frequently than other storm-petrels. Most often seen in small, loose flocks; sometimes rests on the water in a dense group. Eats plankton from the surface of the water.