-6- 
Black-winged Petrel 15 
( Pterodroroa hvpoleuca nigripeimis ) 
Bonin Island Petrel ? (Pterodroma hvooleuca h?rpoleuca ) 4 
White-winged Petrel ( Pterodroma leucoptera j 1 
These small Pterodroma were almost without exception reporded south 
of the South Equatorial Current in the Central Pacific Water Mass_. This in¬ 
dicates their preference of a distinct water type. These forms will al¬ 
ways pose identification problems and unless the individuals are close 
and viewed under good conditions, specific designation is hardly more than 
a guess. The sightings referred to Bonin Island Petrels ? could well have 
been the race P.l. brevipes of the WTiite-winged Petrel. At least 13 other 
sightings were recorded simply as small 
* 
Cooks Petrel ^ 
( Pterodroma cooki i) 
Excellent views of a single individual were made on 1 April at the 
mouth of the Gulf of Califorrma. I am reasonably certain I saw^none of 
these in the concentrations of similar small Pterodroma near 20 S, 
Harcourt's Storm Petrel ( Oceanodroma castro ) ? 8 
Leach's Storm Petrel ( Oceanodroma leucorhoa ) 178 
Galapagos Storm Petrel (Oceanodroma tethys ) . 15 
unidentified white-rumped storm petrels 213 
Except for abundant coastal species, white-rumped storm petrels were 
second in numbers only to the Sooty Tern. High densities were recorded in 
both*the North and South Equatorial Currents. Numbers dropped off consid¬ 
erably south of 5*^8 latitude. . ^ ^ 
Despite the elaborate ."Keys" and other identification aids proposed by 
Project members, a white-rumped storm petrel at 100 yards is just thatl The 
fantastic amount of variation in rump patches of Leach's easily covers tne 
ranges of this character of all other white-rumped species. In time of molt 
Leach's tails are not necessarily forked; they occasionally may^daoble their 
feet as do Wilson's; and their flight may be as erratic or as slw as any 
of the other species, depending upon their mood, I still maintain that ohe 
"Crossin Method" » of field identification of this group is the only sure 
way. By this method 125 specimens of white-rumped storm petrels were taken 
during the present cruise. Examination of this large series o^y empha^zes 
the folly of attempting to apply specific designation to all sighted birds. 
Of the 125 specimens, 112 were ^each's and 13 were Galapagos Storm Petrexs. 
No Harcourt's Storm Petrels were collected and I am uncertain as to whetner 
this species was even seen although I tentatively identified at least eigh 
sightings as belonging to this species. , . ^ 4 .v, + 
The great variation in size throughout the Leach sample indicates tha 
at least two, and possibly more than two races are represented, ^ceeding- 
■ ly pmnn birds were taken which weigh less than many of the tiry Galapagos 
and exhibit most characters of this latter species (for a classi^l e:mm- 
ple, see specimen Field Series # 105225). Such individi^ls wo^d be im¬ 
possible to distinguish from typical Galapagos in the field. On certain 
* This metnod avoids the need of heavy, cumbersome field glasses. A light 
weight shotgun and plenty of ammo suffice, • 
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