amateur vs bird watcher

amateur and bird watcher both are nouns.

Word	Noun	Adjective	Verb	Adverb
amateur	Yes	Yes	No	No
bird watcher	Yes	No	No	No

As nouns, bird watcher is a hyponym of amateur; that is, bird watcher is a word with a more specific, narrower meaning than amateur:

amateur: someone who pursues a study or sport as a pastime
bird watcher: a person who identifies and studies birds in their natural habitats

Other hyponyms of amateur include birder, dabbler, dilettante, sciolist, hobbyist.

amateur (noun)	bird watcher (noun)
someone who pursues a study or sport as a pastime	a person who identifies and studies birds in their natural habitats
an athlete who does not play for pay	a zoologist who studies birds

amateur (adjective)	bird watcher (adjective)
engaged in as a pastime
lacking professional skill or expertise