birdwatcher       
noun [ C ] uk/ˈbɜːdˌwɒtʃ.ər/ us/ˈbɝːdˌwɑː.tʃɚ/
 观鸟者,在大自然观察研究鸟类的人
someone who studies birds in their natural environment as a hobby
  To the trained eye of a birdwatcher, no two eagles look the same. 对训练有素的观鸟者而言,只要是两只鹰,样子一定会不同。 
 Birdwatchers have seen several seagulls matted with oil. 观鸟爱好者看到了几只身上沾满油污的海鸥 
 See: birdwatching
 - More examples
 - Alan has been an active birdwatcher for 10 years.
 - Crows make birdwatchers anxious because they scare the smaller birds away.
 - An enthusiastic birdwatcher, he decided to become a zoologist after spotting a rare duck.