北海道におけるホシムクドリSturnus vulgarisの飛来状況：渡島半島における初記録と近年の観察記録の増加

抄録

The Common Starling Sturnus vulgaris is a winter visitor to Japan, with more records in the western region. In Hokkaido, this species is known as an accidental visitor, and some reports suggest that the number of observations recorded in the Sapporo region have recently increased. In this study, we first reported our observations of the starling in Oshima Peninsula, southern Hokkaido, where this species had not been previously recorded. We then collected published observation records from 1987, when the first starling was recorded in Hokkaido, until 2018. From these records we examined the distribution of observations of the starling and assessed whether the number of them flying to Hokkaido has increased during this period. The birds were widely observed in Hokkaido, with the number of records occurring more frequently in the Sapporo, Ishikari and Okhotsk regions. The number of observation records was high both in spring (April) and fall (October), suggesting that the birds might visit Hokkaido during their migration. The annual number of observation records showed an increasing trend, which occurred every year from 2004. In addition, the number of birds per observation seemed to increase in recent years, but with high interannual variability. Therefore, careful attention should be paid to the changes in the number of starlings and their distribution throughout Japan, including Hokkaido.