all-over bird density, with large flocks of Sooty Terns and boobies feed¬ 
ing over tuna schools. 
Shearwater/petrels were the dominant group. Wintering and resident 
populations of stom petrels occurred sympatrically making storm petrels 
the second most abundant group. 
Area ’’C" . l4°N-109°W to 3°N-105°W 
This was an arbitrarily chosen area, encompassing several environ¬ 
ments and birds of multiple origin. The northwestern track was charac¬ 
terized by choppy seas, with flocks of Sooty Terns of possible Tres Marias 
origin. The southeastern leg had very calm seas and Leach Stom Petrels 
were the dominant birds. The equatorial counter-current did not support 
the large bird populations found farther west and is evidently less dis¬ 
tinctive at this longitude. 
Sooty Terns were the most abundant species with Leach Stom Petrels, 
Brown Boobies, Red Phalaropes, and Wedge-tailed Sheairwaters occurring in 
significant numbers. Most of the area was influenced by coastal species. 
Appendix "D” is a summary of species and populations observed along the 
coast from Manzanillo to Acapulco. 
Area 30°N 105°W-4°S 105°W and 4°S 112°W-5°N 112°W 
This area is commonly referred to as the Doldrums, and has almost 
identical characteristics across the entire Pacific. It is characterized 
by very calm seas, which are rich in plankton and support large popula¬ 
tions of cetaceans, but relatively few birds. Due to this phenonemon 
the ’’equatorial doldrums” are of special ornithological interest. Ex¬ 
planations for the lack of birds may be due to a lack of fish, or the lack 
of wind which most pelagic species appear to prefer. In any case careful 
analysis of environmental data should help to answer important questions 
on distribution and habitat of pelagic birds. 
# 
Leach Stom Petrels were by far the most abundant birds. Red 
Phalaropes were recorded regularly but not commonly. Other species were 
recorded on the fringes of the area, and were probably only passing throu^ 
Area ”E” . 5°S-20°S along lO^^’W and 112°W 
Rough seas and high winds prevailed throughout^ this area. Although 
Sooty Terns were the most abundant species present, petrels were an area 
indicator. Several species of Pterodroma were only encountered within 
this area. 
Environment varied from rich zones at 10°S to virtually barren seas 
at 20°S. Birds were found feeding on large schools of flying fish chased 
