■Area D yielded approximately 85 percent fever 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¬ 
faced 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 
&ftd 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. 
