+18 = 21 

ㄓㄨㄢˇzhuǎn

zhuànㄓㄨㄢˋ
  1. )​婉轉鳴叫 」、山谷」。

to sing (of birds or insects)​, to warble, to chirp, to twitter
chanter (oiseaux)​, gazouiller
singen, zirpen, trällern, trillern, zwitschern, schnattern (V)​