Sea Bird Distribution- — K uroda 
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distribution with that of R, tridactyla, in 
map), Lams glaucescens , and Aethia psittac- 
uius. Among migrants, northern breeding 
species such as Nordmann’s Tern, skuas, etc., 
were found mainly in this division in late 
June, and Pterodroma inexpectata represented 
a southern hemisphere migrant. Further sub- 
divisions with different sea bird densities 
were as follows: 
a. Bering Sea waters: Bird density was very 
low but Rissa brevirostris was relatively 
common. Birds of this species contained 
a large amount of body fat, but one col- 
lected specimen of two Rissa tridactyla 
encountered was entirely devoid of fat. 
Possibly both were stragglers. 
b. Attu-Commander Is. waters: Towards the 
Commander Is., the fulmars increased, 
showing clustered distribution around dis- 
carded viscera of whales. Apparently food 
supply was abundant near the islands and 
bird density was high. A big mixed flock 
of Fulmarus glacialis and Puffinus tenui- 
rostris (and of other sea birds and the 
porpoise, Phocaenoides dallii) was de- 
vouring euphausids at dawn, June 23, west 
of Attu, where meeting lines of cur- 
rents occurred and some southerly summer 
winds were blowing. East of Agattu, where 
there was a strong local water current, 
alcids such as Aethia psittaculus and A. 
pusilla were abundant. Rissa tridactyla 
was not uncommon but no R. brevirostris 
was seen. 
c. Transitory waters: A generally pelagic 
zone with medium bird density. Main 
species were: Fulmarus glacialis, P. tenui- 
rostris , 0 . furcata, and O. leucorhoa, as 
well as occasional Pterodroma inexpectata . 
d. S. Kamchatkan offshore waters: Bird dens- 
ity, especially of Fulmarus and P. tenui - 
rostris, was again high and a marked con- 
centration of O. furcata was found. Lunda 
and Uria (mostly U. aalge ) as well as 
skuas ( Stercorarius pomarinus and S. 
longicaudus) became common, while R. 
brevirostris (total seen 113) outnum- 
bered R. tridactyla (total seen 36), June 
25-July 5. 
2. Offshore Kuriles division 
A stretch of sea surface influenced by cold 
winds and waters of the Okhotsk Sea. The 
bird density was sparse, the dominant species 
being Fulmarus as usual O. leucorhoa out- 
numbered O. furcata, which decreased towards 
the south. Lunda was found scattered and 
R. tridactyla occurred, but R. brevirostris was 
not observed. Aethia cristatella was found 
extremely localized off Shinshiru Is. 
B. Offshore Kuriles Convergence 
(180-200 miles offshore) 
Outside the Kuriles cold current a zone of 
convergence was found between the cold current 
and the periphery of the warm current, and some 
demarcating lines were noted. A change in rela- 
tive abundance was noted, O. leucorhoa becom- 
ing the dominant species, and O. furcata and 
Fulmarus as well as Lunda decreased. Diomedea 
immutabilis seemed to be most suited to this 
intermediate temperature zone, while warmer 
adapted species, such as D. nigripes, and Ptero- 
droma solandri (first recorded in this zone) 
began to appear. 
C. Offshore Warm Current Sea Surface 
At a point just north of 41° N., 240 miles 
E.S.E. of Kushiro, Hokkaido, the periphery of 
the warm current was reached; there the sky 
cleared up and the sea was very blue and calm 
with gentle southern breezes (air 22° C. and 
water 15° C). Such fish as the swordfish, 
sharks, and sunfish, which characterize the warm 
current, occurred there, and Phocaenoides dallii 
was replaced by Lagenorhynchus obliquidens, 
while the sperm whale was observed in family 
groups. A radical change in bird species was 
noted. No species occurred in large flocks, which, 
perhaps, was evidence of the scarcity of plank- 
ton, the basic food supply. In this zone D. im- 
mutabilis was replaced by D. nigripes and O. 
leucorhoa by O. castro. Such southern hemis- 
FlG. 2. Distributional patterns of sample species in the Northern Sea division. 
