Small gadfly petrel. Gray upperparts and head, with darker “M” across wings. Underside white, with thin dark wing edge leading into a short diagonal bar cutting into the underwing. Main colonies breed on Mercury, Hen and Chickens, Poor Knights, and Ririwha Islands in New Zealand. Forages in warmer waters off the northern North Island. After breeding, migrates to the central North and Southwest Pacific. Cook’s Petrel is larger and paler but hard to differentiate at sea. Gould’s Petrel has a darker head, giving it a capped appearance, and more extensive dark on the underwing.