Sea Bird Distribution— -KURODA 
57 
87 
Alcidae 
♦ -# Lund a cirrhata 
♦ Fratercula corniculata j 
♦ Cerorhinca monocerata. 
° Uria sp. 
■ Synthltboramphus ^ 
antiquus 
a Synthltboramphus s 
wnmiziiRirmfi & 
a Braciyramphus 
marmoraiUB 
+ Athia pusilla 
x Alhia psittacalcL 
® Athia cristate llcr. 
( For size of mark cf- 5 ) 
Storm Petrels 
°^0 Oceanodroma 
* Oceanodroma, 11 ^ 
a . . leucorhocc 
Oceanodroma 
castro 
A Oceanodromatristrami 
( For siz of mark cf. 5 ) 
3^ Gulls and Skuas i 
c 
to ) 3 C • i 
• Rissa tridadyla 
° Rissa brevirostris \ 
J A ° A 
i / o^a 
j h ^ 
□ Larus glaucescens 
© Larus schistisaqus 
/A aaO* a ^ 4 , 
\ j *o • o# #x m 
1 . / AA X. □ 
\ r a ^ 
O Larus crassirostris 
/ *° . A x« ^ 
V #0 O A ° 
\y *2 * ^ 
x Sterna hirando. 
lonqipennis ^ 
A A 
O A W 
•A X # 
4 •• 3 
J? 
a Stercorarius 
pomarinus 
a Stercorartas 
Iongicaudus 
■ Catharacta skua 
( For size of mark cf .5 ) 
4 
• 7 Mis cella neous 
species 
• Passerines : 1 Unidentified , 2 
AnthusC?), 3,4 Phylloscopus borealis exami- 
nundus (collected); 5 Locastelia o. ochote- 
nsis (collected), o-Anthus spirio letter 
(collected), 7 Banting sp. 
A Phalaropus falicarius a Lobipes 
lobatus <§) Harlequin Duck (collected.) 
Fig. lb. 
Maps showing the distribution of the birds observed and collected. 
For comparative study of sea bird distribu- 
tion, specific relative abundance within a sea 
zone and zonal relative abundance inclusive of 
all species occurring in the zone, will be con- 
sidered. The distribution of sea birds is subject 
to three general sources of variation: zoo- 
geographic (endemism), ecological (food and 
temperature dependent), and seasonal (physio- 
logical cycle and migration). These factors in- 
fluence the occurrence of various species and the 
relative abundance of birds in different sea 
zones. 
Each species has its range of physiological 
tolerance to temperature, both in air and in 
water, although this is less strict in some species 
and varies seasonally to some extent. Further- 
more, a few individuals may stray out of this 
range, and long-distance migrants of cold cur- 
rents cross the tropical seas. Within a preferred 
temperature sea zone, the food supply and inter- 
specific relation in some cases determine the 
local relative abundance of sea birds and form 
a basis for subdividing the sea zone. 
The specific relative abundance of sea birds 
within a sea zone was estimated by the "specific 
lowest density” per hour (of Elton, 1953: 51), 
which is: 
2 Number of birds observed per hour 
Total number of observation days 
In this calculation of lowest density are in- 
cluded the days on which the species has not 
been recorded. Therefore, it is lower than the 
