5 all-over bird density, with large flocks of Sooty Terns and boobies feeding over tuna schools. Shearwater/petrels were the dominant group. Wintering and resident populations of storm petrels occurred sympatrically making storm petrels the second most abundant group. Area "C". 14°N-109°W to 3°N-105°W This was an arbitrarily chosen area, encompassing several environments and birds of multiple origin. The northwestern track was characterized by choppy seas, with flocks of Sooty Terns of possible Tres Marias origin. The southeastern leg had very calm seas and Leach Storm Petrels were the dominant birds. The equatorial counter-current did not support the large bird populations found farther west and is evidently less distinctive at this longitude. Sooty Terns were the most abundant species with Leach Storm Petrels, Brown Boobies, Red Phalaropes, and Wedge-tailed Shearwaters 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 "D". 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 populations of cetaceans, but relatively few birds. Due to this phenomenon the "equatorial doldrums" are of special ornithological interest. Explanations 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 Storm 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 through. Area "E". 5°S-20°S along 105°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