Sea Bird Distribution— Kuroda 
67 
SUMMARY 
1. During a research cruise from Japan to the 
west Bering Sea, June to July, 1954, a sea bird 
census was made. 
2. As an indication of population density, the 
number of birds observed per hour was used. 
The speed of the ship averaged 7 miles per 
hour, and the number of birds per square mile 
was calculated for sample sea divisions. 
3. Attempts were made to show a correlation 
of bird density with food supply. 
4. Distribution of sea birds is subject to zoo- 
geographic factors ( endemism ) and to eco- 
logical factors (food and temperature), as well 
as to seasonal physiological cycles and move- 
ments. Sea zones were divided according to air 
and water temperatures and to relative abun- 
dance of sea birds. 
5. The distribution pattern was different for 
different species of sea bird. Flocking species, 
although generally distributed, showed a clus- 
tered pattern, concentrating where food was 
abundant, while solitary species were distributed 
at random, since sparse amounts of food suffice 
for them. 
REFERENCES 
Austin, O. L., Jr., and F. Wilke. 1950. Japa- 
nese Fur Sealing. Nat. Resources Sect., GHQ, 
Rep. 129. Tokyo. 
Canada, Japan, and U. S. Governments. 
1954. Distribution and Food of North Pacific 
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Fisheries Bureau, Tokyo). 
Elton, C. 1932. Territory among wood ants 
(. Formica rufa L.) at Picket Hill. J. Anim. 
Ecol. 1: 69-76. (Also presented in Elton, C. 
1953. The Ecology of Animals. 97 pp. Meth- 
uen, London. The reference quoted is to p. 51 
of this book.) 
Kuroda, N. 1955. Observation on pelagic birds 
of the northwest Pacific. Condor 57(5): 290- 
300. 
1956. Records of pelagic mammals ob- 
served in the northwest Pacific. J. Mammal. 
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Odum, E. P. 1954. Fundamentals of Ecology. 
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of North Pacific albatrosses. Auk 68(2); 
227-235. 
Torii, S. 1952. Methods of measurement of in- 
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(In Japanese.) 
