Distribution of Black-footed Albatross, Diomedea nigripes , 
off the West Coast of North America, 1949 and 1950 1 
J. L. McHugh 2 
Since the oceanographic surveys of the 
California Cooperative Sardine Research Pro- 
gram began in March 1949, records have been 
kept of the numbers of albatrosses seen at 
each station. At monthly intervals the ships 
have covered an area approximately 1,300 
miles long by 400 miles wide. The patterns 
of stations occupied, differing somewhat from 
cruise to cruise, and altered considerably in 
1950, have been figured by McHugh (1950), 
Anonymous (1950), and McHugh and Ahl- 
strom (1951). 
These albatross observations have formed 
a part of the objective, conceived early in the 
development of the research program, to 
study as many phases of the biology of the 
region as possible. Felin and Marr (1951) 
already have pointed out the importance of 
these subsidiary investigations in relation to 
the main purpose of the sardine program. 
INDICES OF ABUNDANCE 
Usually, counts were made shortly after the 
ship hove to at each station, and again just 
before departure. The second count com- 
monly, but not always, exceeded the first 
(McHugh, 1950). The indices of abundance 
used here are based on the maximum numbers 
of birds observed at each station. For obvious 
1 Contributions from the Scripps Institution of 
Oceanography, New Series, No. 805. Manuscript re- 
ceived February 10, 1955. 
2 Director, Virginia Fisheries Laboratory, Gloucester 
Point, Virginia. 
reasons, no record was made at stations occu- 
pied during darkness, although albatrosses 
sometimes were seen at night (McHugh, 
1952). 
It is believed that several factors other than 
relative abundance may influence the counts. 
Birds may follow a ship as it cruises between 
stations, but it is not believed that the Black- 
footed Albatross travels great distances in this 
way (Miller, 1942; Thompson, 1951). The 
tendency to congregate about the motionless 
vessel may vary with weather conditions, es- 
pecially if the frequency and duration of 
soaring flight is related to wind force, al- 
though an attempt to analyse the data along 
these lines produced no clear-cut relationship. 
Furthermore, counts may tend to increase 
during the day (McHugh, 1950) or when the 
ship is in an area for longer periods (Yocom, 
1947). The visual acuity of birds and ob- 
servers is affected almost certainly by atmos- 
pheric conditions and wind. The many 
observers undoubtedly varied in interest and 
in acuteness of vision. For these reasons, 
counts at adjacent stations were averaged by 
dividing the survey area into 21 blocks, by a 
grid of three blocks east to west and seven 
north to south (Fig. 1). These blocks are not 
equal in area, for the species seldom ap- 
proaches within sight of shore, and often is 
not present in great numbers at the inshore 
stations. To avoid masking the reduced 
abundance near shore, the seven inshore 
blocks were chosen as far as possible to in- 
Wniim 
375 
