PRELIMINARY REPORT 
EASIROPAC CRUISE NO. JO 
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 
coastal 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 l). 
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 -ompleted in 
this area. Thirty species were recorded with greatest numoers of 
both species and individuals occurring along the coast of southern Baja 
California from Vizcaino Bay south to Cape San Lucas. Northern 
Phalaropes far outnumberd 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. 
