$Ardenna gravis Bent,1922,Bulletin of the U.S. National Museum,121,p.65.
Marine. Generally occurs in cold offshore & pelagic waters, Breeds on slopes,often covered with dense vegetation,mainly near sea,but also inland up to 1500m
"Starts Oct." (HBW,1,p.254)
Transequatorial migrant,moving into North Pacific(where more abundant) and North Atlantic. Large numbers head first into northwest sector of these oceans,then progressively move east following prevailing winds to reach west coasts of North America and Europe late in local summer. Many thus complete wide loop before returning to breeding islands. Most South America birds may move fairly directly up and down west coasts of Americas.Some birds remain in southern oceans over winter.