378 
PACIFIC SCIENCE, Vol IX, October, 1935 
/30° /2S° 
"////""/XT 
jj Br/t/sh 
^ CoJumb/3 
SSvT 
Project Offshore A 'o. 
August /. 950 
j Washington 
D 
Fig. 2. Distribution of Black-footed Albatrosses off 
the British Columbia and Washington coasts in August 
1950. Legend as in Figs. 1 and 3. The contours were 
drawn according to the numbers of birds at each 
station. 
though Cruise 20, in November 1950, ex- 
tended the coverage southward almost to 20° 
N., no albatrosses were seen at this time off 
the entire Baja California coast. Later cruises, 
reaching this latitude in all seasons, may be 
expected to define more accurately the south- 
ern extent of the species range. 
To the northward, the Black-footed Alba- 
tross is common off British Columbia and 
Alaska, and has been seen irregularly in the 
Bering Sea (Kenyon, 1950). Counts supplied 
through the cooperation of Dr. J. L. Hart and 
R. J. Waldie from off the coasts of Washing- 
ton and British Columbia in August 1950 
range from 1 to 24, and average 13 birds 
per station (Fig. 2). 
To the westward, in 1949 and 1950 only one 
cruise extended more than about 400 miles 
offshore. On this cruise, numbered 18, in 
September 1950, the maximum count in the 
region outside the grid defined in Figure 1 
was six birds at station 70.220. Diomedea 
nigripes is found across the entire Pacific, how- 
ever, for it breeds in the mid-Pacific islands 
in winter and spreads over the north Pacific 
at other seasons. 
SEASONAL DISTRIBUTION AND ABUNDANCE 
In 1949 and 1950 Black-footed Albatrosses 
were about twice as abundant in the survey 
area over the period March to May as in any 
other month. The distribution of counts in 
1949 (Fig. 1) suggests that the decrease in 
abundance in the summer months is caused 
by a general northerly migration, for the 
greatest density of birds was encountered off 
Point Conception in March, off San Francisco 
in April, and off the Columbia River in May, 
an average northward shift of about 300 nau- 
tical miles per month. Not until October did 
similar concentrations appear again within the 
survey area, this time in a region well offshore 
from Cape Mendocino. In 1949 also, there 
appeared to be a general shift of the popula- 
tion from inshore in spring to offshore in fall. 
In 1950 (Fig. 3) there were less definite 
indications of a progressive northerly migra- 
tion, although the index of abundance was 
highest in March. If a northward movement 
did take place, it probably occurred .earlier 
than in 1949, and there is some evidence that 
the return movement began in May, for the 
birds were more abundant off Cape Blanco in 
May, and off San Francisco in June than at 
any other period in 1950. Furthermore, in 
July and August the greatest densities were 
observed in the region between San Francisco 
and Point Conception. The 1950 season dif- 
fered from 1949 also in that, from May to 
August inclusive, more birds were seen in- 
shore and less at the offshore stations. 
FACTORS AFFECTING ALBATROSS 
DISTRIBUTION 
Variations in the numbers of Diomedea ni- 
gripes observed off the shores of North Amer- 
ica have been attributed to various factors. 
Miller (1940) found these birds concentrated 
over a "cold tongue” of sea water, rich in 
nutrients and plankton. Thompson (1951) 
reported that the species was more abundant 
east of the 135th meridian, and showed that 
the increasing numbers of birds seen between 
