OCEAN WATER TYPES 
Although the writer is not well versed in oceanography, the following 
discussion is attempted because the effect water types have on bird dis¬ 
tribution is well known. Before any correlations are attempted a general 
discussion is prerequisite. 
Probably the most graphic water type surveyed on this cruise was the 
North Equatorial Countercurrent. Although I am not certain of the boundaries 
some of the oceanographic data suggest that on the western leg of the cruise 
the north boundary was at about l4-°^3*N “ 119°10 f W. In this area there was 
a significant change of salinity and also the writer observed "a line of 
marked current activity” at about 1735 hours (local-+7) on 22 October. 
The southern boundary of the North Equatorial Countercurrent was also 
indicated by a line of marked current activity. Oceanographic data also 
substantiated this observation with marked salinity and temperature changes 
having been recorded at 03°59 T N “ 119°10 T W. 
Travelling eastward and then north along 112 o 10 T W, the southern bound¬ 
ary of the countercurrent was again visually observed as well as substant¬ 
iated by oceanographic data at 04- o 53 ! N. The northern boundary was not 
visually observed, and oceanographic data as available at present do not 
make the boundary unquestionably clear. However there were rather marked 
salinity and temperature changes near 15°N - ll 8 °W. Whether this was the 
countercurrent boundary or some other water type is not clear. Avian 
changes, however, suggest that it may have been the boundary and it is 
considered as such in this report. 
On the remainder of the cruise the countercurrent boundaries were not 
visually observed. Oceanographic data suggested boundaries near 11°N and 
between 1° and 2°N along 105°10 T W longitude, and was somewhat confused 
along 098 °W. These unclear definitions in the eastern portions of the 
survey area are not surprising as it is near the terminus of the North 
Equatorial Countercurrent and is also near the area where the eastward 
moving equatorial undercurrent breaks and diverts in the vicinity of the 
Galapagos Islands. Thus with the data available to the writer at present 
the water type boundaries in the eastern areas should remain indefinite. 
COASTAL WATERS 
The survey area along the Mexican coast between Manzanillo and Acapulco 
is separated for discussion purposes only, and is probably incorrectly con¬ 
sidered a single water type. The oceanographic data collected on three 
five-hundred mile transects through the area are confusing and suggest 
several influences with upwelling probably being major. 
Along the central and northern Baja coastline the California Current 
is without doubt the major influence. Although few oceanographic data 
were collected, the junction of the Current and southern water appears 
to have been off Magdalena Bay where high seas, high winds, and spectacular 
numbers of animals were recorded. 
