Ardenna gravis
Large shearwater with distinct, marked, dark cap and white collar. Blotched belly and underwings. White upper tail-coverts forms a horseshoe mark, but note that Cory's Shearwater may show the same. Dark patch at side of neck. Bill dark. Flight action powerful, with alternating glides and rapid bursts of beats with stiff wings. Seldom soars.
Calls at breeding ground a deep, soft, moaning "oooh-aahh" ("surprised or shocked old lady"). Tone fairly clear, and pitch rising and falling.
Wikipedia: map (se also Xeno-canto below)
Birdlife ecology
