PRELIMINARY REPORT EASTROPAC CRUISE NO. 30 JUNE - JULY, 1967 Patrick J. Gould During the period 14 June through 02 August, 1967, pelagic sea-bird observations were conducted aboard the R/V David Starr Jordan in the Eastern Pacific Ocean. This was in co-operation with EASTROPAC, an oceanographic investigation of the Eastern Tropical Pacific Ocean by the United States, Mexico, Ecuador, Peru, and Chile. These investigations have been discussed in detail in previous reports and will not be repeated here (See Woodward, Miscellaneous Pelagic Cruise No. 8, and Bulmer, Miscellaneous Pelagic Cruise No. 9). Diurnal observations (sunrise to sunset) were conducted only while the ship was underway, although spot checks were frequently made while the ship was stationary or during nocturnal hours. Specimen collecting and photography were conducted where possible. A total of 3,072 miles and 299.3 hours of observations were completed in 46 days. In high density costal areas accurate counts were impossible and only species identification and generalized population estimates were attempted. TABLE 1 presents a brief summary of these observations. Density values are in birds per square mile (BSM) and were derived from previously established visual distances of different species groups. Frequency values are given in terms of sightings (one or more birds acting as a unit) per hour. Since the oceanographic data has not yet been completely analyzed, all correlations with the bird data are to be considered preliminary and subject to future revision. The coverage area extended from San Diego, California, south to 03 degrees South, and from 119 degrees to 97 degrees West (See FIGURE 1). In this area over 28,000 birds of at least 46 species were recorded. Many different oceanographic and/or climatic conditions exist within this large area. Because of the preliminary nature of the oceanographic data, and with a concession to easy handling of data, I have divided the whole area into four rather heterogeneous parts; COASTAL, within 150 miles, or one days observation period, from the coast; NORTHERN PELAGIC, all areas over 150 miles from land north of 12 degrees North; COUNTERCURRENT, between 04 and 12 degrees North; SOUTHERN PELAGIC, between 03 degrees South and 04 degrees North. COASTAL: 339 miles and 31.9 hours of observations were completed in this area. Thirty species were recorded with greatest numbers of both species and individuals occurring along the coast of southern Baja California from Vizcaino Bay south to Cape San Lucas. Northern Phalaropes far outnumber any other species although Manx Shearwaters were abundant and of much more regular occurrence. TABLE 2 shows the distribution of all species observed within this area.