Professor Chang Hsueh-wen of NSYSU's biology department says that some birds, such as the Chinese bulbul, seem to have only one song, but in fact that song includes a great many variations on a basic theme.
中山大學生物系教授張學文表示，有些鳥兒唱歌聽起來只有一個音調，比如白頭翁的歌聲，但其中聲頻婉轉多變，彷彿變奏曲。