island was therefore considered to be 75 percent of the number of birds 
visible on the aerial photographs. This method is believed to be quite 
accurate for censusing islands with open terrain; on islands with con- 
siderable scrub growth, a large number of birds will be missed, and 
ground counts are essential. On two islands (Nihoa and Kaula), owing 
to the ruggedness of the terrain, the small number of albatrosses 
present, and the possibility of confusion with boobies, no counts 
could be made from the photographs. The figures presented for these 
islands are rough visual estimates made with 7x50 binoculars from the 
open hatch of the aircraft. 
Ground counts were conducted in two ways: (1) Total counts 
of all nests were made where practical (black-footed albatrosses on 
Midway, and both species on Kure), and (2) sample-plot censuses were 
conducted where complete coverage was impractical. On Midway, randomly 
distributed one-fifth-acre circular plots were used. On Laysan Island, 
50-foot-wide strip transects were laid out so as to cover the island 
in uniform fashion. 
Results 
During the 1956-57 season, population estimates included un- 
employed birds known to be on the islands (Kenyon et al. 1958). 
Subsequent studies have shown that the unemployed birds present on the 
nesting islands at any given time are only a small and variable fraction 
of the total unemployed group, as they spend much time at sea. The true 
size of this segment of the population is yet unknown, but it is 
suspected to be much greater than was previously believed. For this 
reason, the population estimates presented here include only the number 
of breeding birds. This gives a concrete figure which can readily be 
determined by counting nests, and which can be compared directly from 
year to year and from island to island. 
A summary of present breeding populations is presented in 
table 1. All estimates have been rounded to the nearest two significant 
digits, as the accuracy of the census methods does not justify more 
precise figures. The total number of nesting birds is approximately 
560,000 Laysan albatrosses and 110,000 black-footed albatrosses. 
It is difficult to determine what this figure means in 
terms of total population -- breeding and nonbreeding. Present data 
suggest that the total, including all categories of unemployed birds, 
is at least three times the number of birds nesting in any one season 
(see section on Studies of Control Methods - large-scale killing 
program). On this basis the total world population of Laysan albatrosses 
is tentatively estimated at 1,500,000, and that of black-footed 
albatrosses at 300,000. (This is over 100 percent more than the world 
populations of each of these species estimated in our previous report 
(Kenyon et al. 1958) owing to the change in our concept of the size of 
the portion of the population at sea.) 
