5 
Manx Shearwater ( 
’’Manx Type Shearwater ^Total Observations - 5>193 
The large flocks of Manx Shearwaters observed on 5 June within 15 
miles of the Manzanilla/Acapulco coast account for nearly 60 percent of 
the total birds (all species) seen. Feeding flocks of 500-plus birds 
were encountered at 2-3 mile intervals during an afternoon of skiff work 
there. Birds were clumped densely on the water surface and appeared to 
be feeding actively. Most birds were in obvious molt with gaps showing in 
the flight feathers. Birds of the Manx/Audubon’s type were regularly seen 
from the Gulf of California to the Gulf of Panama. While I believe that 
most of the Manx types seen were indeed Manx, several times I suspected 
that Audubons were present. No Audubons were positively identified, however. 
Christmas (island) Shearwater Total Observations - 20 
Puffinus Nativitatis 
m 
I can find no previous record of this species for the eastern Pacific 
coast. Each of the large feeding flocks of Manx Shearwaters investigated 
off the coast on 5 June seemed to have 1-3 of these birds. One female with 
a granular ovary was collected. Without the use of the skiff I am confident 
this species would have been completely overlooked. 
Cooks Petrel Total Observations - 184 
Cooks Petrel was the dominant species observed between Guadalupe 
Island and the tip of Baja, California. Several large flocks were found 
milling about on the water near what appeared to be the edge of rising 
water cells. Storm Petrels were also plentiful in these flocks. One 
female with granular ovary was taken the first of June. Most birds were 
in heavy wing molt with confusing white patches and streaks visible from 
above. 
Leachs Storm Petrel Oceanodroma leucorhoa 
North of about 12°N most of the ’’White-rumped’ Storm Petrels are prob¬ 
ably this species. For three days in the vicinity of Guadalupe Island the 
dark-rumped population, 0. 1. socorroensis , was present at about one-fifth 
the density of the white-rumped form. One female socorroensis with enlarged 
gonads was collected approximately kO miles south of Guadalupe Island on 
1 June. After a 1,500-mile gap ’’Dark-rumped” Storm Petrels were again seen 
off Panama. It is possible that these were Least Storm Petrels. 
Galapagos Storm Petrel Oceanodroma tethys 
When three days out of Panama ’’White-rumped” Storm Petrel sightings 
increased again after a dropping off from the Leachs peak off Lower Baja. 
On 9 June ’’White-rumped” Storm Petrels were noted following the ship’s wake 
and by 11 June up to 25 at a time were following astern. Most, if not all, 
of the ’’White-rumped” sightings below about 12°N are likely this species. 
I have seen no mention of ship-following tendencies in other sources. 
