Black-footed Albatross — McHugh 
377 
elude only the inshore stations on each line. 
Their offshore limit is a line running roughly 
parallel to the coast about 40 nautical miles 
westward of the major promontories. The 
second series of blocks extends from the 
western boundary of the first and has a width 
of about 160 miles east to west; the third is 
approximately equal in width to the second. 
Each of the seven inshore blocks, about 9,600 
square nautical miles, is roughly one-quarter 
the average area of the remainder. The in- 
shore blocks each contained two stations in 
1949, and an average of six in 1950; each 
offshore block contained an average of nine 
stations in each year. 
As a monthly index of abundance, all counts 
within each block were averaged, a process 
designed to minimize many of the most seri- 
ous sources of error. These indices may be 
defined as representing the best available es- 
timate of relative monthly abundance within 
each block. There is little point in expanding 
these estimates into a measure of the total 
number of birds present in the area, for there 
is no adequate basis for determining the ab- 
solute density of birds per unit area that each 
count represents. Assuming, however, that 
all birds within a ten-mile square collect 
around the ship while it occupies a station, 
the total number of Black-footed Albatrosses 
present within the region surveyed in May 
1949, the month in which most birds were 
observed, was close to 100,000. This estimate 
is not inconsistent with the results of the 
census made by Fisher (1949) on the Island 
of Midway. 
The cruises have not always covered the 
entire region included within the station pat- 
tern. Sometimes parts of the area have been 
missed on account of adverse weather condi- 
tions or mechanical breakdowns. Sometimes 
the station coverage has been shifted accord- 
ing to plan, in response to seasonal changes 
in the location of sardine spawning. Blocks 
7 to 18 inclusive were occupied on most 
cruises in 1949 and 1950, and it is possible 
to calculate an index of abundance for the 
TABLE 1 
Indices of Abundance of Black-footed 
Albatrosses in the Region Covered by 
Blocks 7 to 18 Inclusive 
MONTHS 
INDICES OF 
ABUNDANCE 
1949 
1950 
February 
63 
March 
113 
April 
132 
66 
May 
106 
74 
June 
86 
87 
July 
60 
62 
August. 
78 
61 
September 
46 
25 
October 
66 
November 
59 
waters off the California coast by summing 
the indices for these blocks (Table 1). How- 
ever, it would be advantageous to discover a 
more restricted area that would reflect the 
abundance of birds equally well. Block 11 
was chosen because it is sufficiently far north 
to contain relatively large numbers of alba- 
trosses, yet close enough to an important 
sardine spawning area that it may be expected 
to be traversed on most, if not all, cruises. 
A high and statistically significant coefficient 
of correlation was obtained between the 
monthly indices for block 11 and for the 
larger area exclusive of block 1 1 (r = +0.863, 
P much less than 0.01). In view of the many 
possible sources of error to which these in- 
dices are subject, it is concluded that the 
relative abundance of birds in block 11, lying 
west of Point Conception, is indicative of the 
relative abundance off the entire California 
coast. 
GENERAL DISTRIBUTION 
Thompson (1951) has observed Diomedea 
ni gripes as far south as 15° 40' N. in the Cen- 
tral Pacific. Along the west coast of North 
America, however, the species has never been 
observed in great abundance south of Cedros 
Island, off the coast of Baja California. Al- 
