Western Bluebird

...The female's head and back are gray-brown. The male of the Western Bluebird, S. mexicana , which lives west of the Rocky Mountains, has reddish-brown shoulders. The male of the Mountain Bluebird, S. currucoides , which lives in the mountains of the West, is particularly beautiful, with pale blue underparts and bright blue aboveparts.

*Some of the terminology that refers to "western bluebird" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…雌の頭と背は灰褐色。ロッキー以西のチャガタルリツグミS.mexicana(英名western bluebird)は雄の肩が赤褐色である。西部の山にすむムジルリツグミS.currucoides(英名mountain bluebird)は雄の下面は淡青色，上面も明るい青色でとくに美しい。…

※「western bluebird」について言及している用語解説の一部を掲載しています。

出典｜株式会社平凡社世界大百科事典 第２版について | 情報