Sooty and Slender-billed Shearwater ( Puffinus griseus and P. tenuirostris ) 
Because these two species are easily confused all sightings were 
called Sooty/Slenderbills. However, of the few birds that were seen well, 
none were Slenderbills. 
Most of the sightings (excepting those off the Ba.ja Peninsula) were 
of birds gravitating towards the southeast. 
Juan Fernandez Petrel ( Pterodroma externa ) 6 collected 
All of the birds which were seen well were identified as the sub¬ 
species externa and the writer is convinced that there were no cervicalis 
in the area. The distribution was somewhat confusing, but increasing 
abundance from east to west was evident, especially in the countercurrent 
area where the highest densities for the cruise were recorded. Although 
Wedge-tailed Shearwaters were present and most abundant in the same area, 
a day to day comparison of ratios demonstrates that there was little cor¬ 
relation of numbers between the two species. That the two have different 
ecological requirements may also be inferred from a comparison of the 
eastern distribution within the survey area. Whereas Wedge-tails were 
found along the easternmost portions of the track, no P. externa were 
seen east of 105° west longitude. Further suggestion of ecological re¬ 
quirements may be inferred from the north-south distribution of the two 
species. Virtually no Wedge-tails were seen south of the southern 
border of the Worth Equatorial Countercurrent, whereas Juan Fernandez 
Petrels were seen as far south as the cruise track went. 
Six specimens of Juan Fernandez Petrels were collected along the 
westernmost portion of the cruise. All were of nonbreeding age, had 
heavy body molt, and were in a light fat condition. 
Cook's Petrel ( Pterodroma cookii ) 
A few birds of this species were seen about three hundred miles west 
of Ba.ja in mid-October. Although only a few were seen, there was some 
suggestion that they were in southeasterly migration. 
Black-winged Petrel ( Pterodroma hypoleuca nigripennis ) 
A total of 3 k birds was identified as this subspecies between five 
and fifteen degrees north latitude on the western leg of the cruise. There 
was no suggestion that they were migrating. 
It is interesting and perhaps significant that the range met but did 
not overlap the range of the White-winged Petrel (P. leucoptera ) recorded 
on the survey. It is also significant (?) that no hypoleucans of the 
subspecies hypoleuca were recorded on this cruise; they were said to have 
been present in approximately the same area in August-September. 
