A survey of sea birds of Teuri I., Hokkaido, with notes on land birds

Abstract

During May 27-31, 1963, the author made a trip of sea bird survey to Teuri I., Hokkaido. This island, known as natural monument of sea bird colonies, is situated in Japan Sea with another island Yagishiri in 44.4 N, 141.3 E, 28km west of middle Hokkaido. Full time watch of sea bird distribution was made on ferry between the island and Tomamae, the port on Hokkaido coast (Table 1, Fig. 1). The only sea bird other than those breeding on Teuri and commonly found was Puffinus griseus.
The island has 7 miles of coastal line and is generally flat but gradually elevated on the NW coast ending as gigantic cliffs extended along more than 2km, with famous Akaiwa Rock at SW point. A few other isolated rocks are along the coast. These part form a sprendid mixed colony of sea birds. The species and estimated number of these birds breeding there were as follows: Larus crassirostris 50.000, Larus schistisagus 100, Uria aalge (possibly no U. lomvia) 8.000, Cepphus carbo 3.000, Cerorhinca monocerata 100.000, Synthliboramphus antiquus a few (?) (Murata 1957 reported as 500), Phalacrocorax capillatus 100.
The conspicuously dominant species almost all over the colony is L. crassirostris which arrives the island in late December laying during May and leaves in late July. But far more, possibly twice or even three times, numerous is the Hornbilled Puffin Cerorhinca monocerata whose burrows occupied the entire upper soily part, average 30 meters in vertical width. The burrows, typically semicircular (dome-shaped) with the hight 10cm and diameter 14cm and more than a human arm length deep, were almost evenly distributed with the density of 6-14 along the distance of ten meters, 170 and 183 within two 10 meter squares. Where abundant and without rocks, only the bandles of stronger grasses, Poa macrocalyx and also Adenophora triphylla in western part, were left at somewhat the same distance (70-100cm) but at very windy tops of the cliff even these grasses had disappeared and burrows were found in desert-like sandy soil.
By ferry boat observations, the daytime feeding sea-surface of this nocturnal breeder was confirmed at anchovy netting area about 25-26 miles from the island not far from Hokkaido coast. In the early morning all the flocks were flying out to this sea-surface where floating groups were found. In the evening, they returned to the island flock after flock, somewhat like the starlings coming back to its roost! Toward dark (it was a foggy evening), a few birds came over the top of the cliff with great sounds of wing beats, suddenly appearing from the fog and circled away in it. Gradually, the birds increased in number and finally landed in the colony (carefully when it is not yet dark). They stood still looking around in an alert posture, but often flew off into the fog again after more or less 15 minutes. Some and not all had one to three anchovies in their bill and here and there such a bird caused a sudden straggle with the Black-tailed Gulls which had been waiting for it to rob the anchovies from its bill before entering in its burrow. The gulls were breeding at rocky edges within the puffin colony and when one finds and dashes to a returning puffin with fish several others would joint at once, while some were constantly flying around low over the puffin colony.
After complete dark, however, the puffins could more successfully return to their burrows to feed the young. They tumbled into the grass on landing and walked to their burrows, but how they can tell their own from those everywhere around is a problem as in the petrels. Many were seen just standing or walking to and fro, and these should include young non breeders. But, unlike the petrels, their colony was quiet, with only a low groom in the nest and rarely the chick voice. It is said that in the early morning they are also resting on the ground and suddenly take off to the sea.