Area D yielded approximately 85 percent fewer birds than its eastern counterpart, Area B. White-rumped storm petrels were dominant. There was a marked decrease in the number of Juan Fernandez Petrels, Black-winged Petrels and Pterodroma species compared to Area C. White-winged Petrels were entirely absent. Area C yielded by far the fewest birds of all of the area (2.5 percent of the cruise total), especially in terms of the number of miles travelled and hours of observation. However, Juan Fernandez, White-winged and Black- winged Petrels all were recorded for the first time on the cruise in this area. Indeed, Area C accounted for 80 percent, 100 percent, and 78 percent, respectively, of the total number of the above three species recorded on the cruise. Mention might here be made of a species conspicuous by its absence in the survey area - the Blue-footed Booby (Sula nebouxii). This species would be expected to occur in Area A near the Central American coast and also near Cocos Island, and in Area B near the Galapagos Islands. This species is undoubtedly liable to confusion with the young of other of the Sulidae, and particularly the writer feels, could be confused with the immature Blue- fac ed Booby (Sula dactylatra). In Area A nine immature dactylatra were identified (none in the vicinity of Cocos Island), four of which were associated with adult dactylatra. The remaining five were individual birds which the observer positively identified. In Area B only two immature dactylatra were noted. They were associated with thirteen adult dactylatra and positively identified. Considering the large feeding flock of Sula sula and Sula dactylatra observed in Area B, the number of birds and their distance from the ship, individual Sula nebouxii in their midst may have been overlooked. The observer can only assert that here, as in the rest of the survey area, this species simply was not noted.