Blue rock thrush

A bird of the family Muscicapidae, subfamily Turdus. It is similar to the brown-eared bulbul in that they are about the same size and look black in certain light conditions, but they are not related at all. It is about 23 cm long. The upper body, head, and chest of the male are dark blue, and the belly is reddish brown in those that breed in Japan, the Korean peninsula, northeastern China, and Taiwan, while those that breed in a long strip of Eurasia from there to the Mediterranean Sea are the same dark blue as the upper body. The female is dark brown overall. In Japan, as its Japanese name suggests, it lives on rocky shores, often on coasts with large rocks and cliffs behind them, building nests in rock crevices and laying 5 to 6 green-blue eggs. It mainly eats small animals on the coast, and is skilled at feeding like a small raptor of the shrike or flycatcher type. Outside of Japan, it does not live on the coast, but instead lives in rocky areas in mountainous areas. From the Yellow River basin in China to Europe, the distribution overlaps with that of the Japanese species, with the White's Rock Thrush, M. saxatilis, which has a white rump similar to the Japanese species.

[Nobuo Takeshita]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

鳥綱スズメ目ヒタキ科ツグミ亜科の鳥。ヒヨドリとは、ほぼ同じ大きさであること、光線によってはともに黒っぽくみえることで似ているが、類縁関係は遠い。全長約23センチメートル。雄の上面、頭部、胸は暗青色で、腹の色は、日本、朝鮮半島、中国東北部、台湾で繁殖するものは赤褐色、それより西、地中海周辺までユーラシアに細長く分布しているものは上面と同じ暗青色である。雌は全体に暗褐色。日本では、その和名のとおり、磯(いそ)にすみ、大きな岩があり背後に岩壁を控えた海岸に多く、岩の割れ目などに巣をつくり、5～6個の緑青色の卵を産む。海岸の小動物をおもに食べ、モズ型、ヒタキ型の小形猛禽(もうきん)類的な採食法も巧みである。日本以外では海岸にはすまず、山岳地帯の岩場をすみかとする。中国の黄河流域からヨーロッパにかけては、日本の本種に似て腰の白いコシジロイソヒヨドリM. saxatilisが重複して分布する。

［竹下信雄］

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