4 
Observations were conducted from the flying bridge or the bow depend¬ 
ing on the type of avifauna present (e.g,, feeding flocks readily observed 
from the flying bridge, storm petrels readily identified from the bow). 
Observational emphasis was placed on sighting and identifying birds near 
the ship. As a result, more distant birds may have been often missed. 
For this reason the total number of categories of observation (e.g., those 
sightings categorized as shearwater/petrel, Pterodroma sp ., and Tern sp .), 
are less than might be expected. 
DISCUSSION 
For purposes of analysis the cruise track was divided into six sec¬ 
tions. Each section was determined on the basis of the fauna present and 
in the most elementary way illustrates six different habitats encountered. 
It is hoped that when final breakdown of environment is available a more 
precise zoogeographic map of the area can be completed. A major fault with 
this preliminary division of the cruise track can be illustrated by area 
"E". This area covers roughly from 5°S to 20‘’S and 11 days of observations. 
Area "E" contains the outer edge of the Humboldt current where bird density 
was 1.159 birds per linear mile on the 3rd of March. But at 20°S the en¬ 
vironment was virtually barren of life and density sank to .078 birds per 
linear mile. 
Each area is dominated by birds from certain land madses which may 
be close or far distant (e.g., area "B", around the Revilla-Gigedo Islands 
is dominated by birds breeding on these islands; area "D" in the equato¬ 
rial doldrums, where dominant birds were Leach Storm Petrels and Red 
Phalaropes from the Arctic'). The daily analysis of each area is illus¬ 
trated in Tables 4-9. 
Area "A". 30°N to 20°N 
This area is influenced by birds from adjacent Baja California, and 
wintering birds from higher latitudes. The dominant species group was 
storm petrels, with gulls second. Shearwater/pelp-els were represented in 
this area by cold-water species or sub-species from the Baja coast and the 
Southern Hemisphere. 
^ . 
* 
Large areas of kelp and an abundance of cetaceans and pinnepeds are 
characteristic of this area. The average surface temperature was 10°C. 
Appendix C contains a sTJoranary of observations along the Baja coast 
on March 23rd and 24thc ^ 
Area 20°N-ll4°W to 12°N-109°W 
Tropical seas siirrounding the Revilla-Gigedo Islands and dominated 
by birds from these islands. The Townsend Shearwater, endemic to this 
area, was the most abundant bird species. Area "B” had the highest 
