separate since they basically agree on all characters mentioned above. 
However, they differ in length of the legs with the legs of a Wilson T s 
generally extending beyond the tail when it-flies. At other times it 
will dabble its long legs in the water. 
Flight may also be a useful character but I did not see enough 
Oceanites to be sure how to tell them from Oceanodroma. However, I did 
see a flight difference between Leach T s and Galapagos’ Storm Petrels. 
Leach’s flies like a small nighthawk with deep wing beats while tethys 
has a stiff wing beat due to the smaller wings of this species. 
I can find no plumage or size characteristic to separate Black Storm 
Petrels from Markham’s Storm Petrels in the field. The area of occurrence 
(Markham’s in the colder water along the equator) and the ship following 
tendency of the Black Storm Petrel were used to identify these species in 
the field. They are both smaller than the Socuy Storm Peurel of the 
4 
central Pacific and larger than dark-rumped Leach's from which they also 
differ in having a more deeply forked tail. 
FIGURES 11-13 show the distribution of these Storm Petrels. It is 
likely that many of the unidentified Oceanodroma on the western two legs 
along the equator were Harcourt’s which I overlooked at the time. 
White-faced Storm Petrel ( Pelagodroma marina ) 
This species was fairly common near the equator on the outer two legs 
but not found near the Galapagos. Competition with the resident storm 
petrels probably excludes it from this area- 
In the region where they occurred, sea surface temperatures were less 
than 20°C which is possibly a limiting factor in .the species. In early 
summer they were not found here when the temperatures were well above 20°C. 
Blue-faced Booby ( Sula dactylatra ) 
Red-footed Looby (Sula sula) 
Adults '^f eoth these species were members of eastern Pacific population 
