Whistler

...A general term for birds of the passerine order, family Muscicapidae, subfamily Pachycephalinae. Because their cry is a whistle, they are also called whistlers or bellbirds in English. They also have large, round heads, so are called thickheads, and some species have beaks similar to those of a shrike, so they are also called shrike-thrush.

*Some of the terminology that mentions "whistler" is listed below.

Source | Heibonsha World Encyclopedia 2nd Edition | Information

…スズメ目ヒタキ科モズヒタキ亜科Pachycephalinaeの鳥の総称。鳴声が笛声なので，英語ではwhistler,bellbirdなどの名がある。また丸く大きな頭をもつのでthickhead，種によってはモズに似たくちばしをもつものもあるのでshrike‐thrushとも呼ばれる。…

※「whistler」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