bird of passage         
noun [ C ] uk/ˌbɜːd əv ˈpæs.ɪdʒ/ us/ˌbɝːd əv ˈpæs.ɪdʒ/  birds of passage
 UK候鸟 
a bird that migrates (= moves from one area to another when the season changes)
  漂泊不定的人;过客
a person who stays for only a short period of time in one place, job, etc.
  At present the organization has to rely on young, inexperienced graduates who are usually birds of passage. 目前该机构不得不依赖没有经验的年轻毕业生,可这些人通常会跳槽。