songster vs singer

songster and singer both are nouns.

Word	Noun	Adjective	Verb	Adverb
songster	Yes	No	No	No
singer	Yes	No	No	No

As nouns, singer is a hypernym of songster; that is, singer is a word with a broader meaning than songster:

Other hypernyms of songster include vocaliser, vocalist, vocalizer.

songster (noun)	singer (noun)
any bird having a musical call	a person who sings
a person who sings with skill
a composer of words or music for popular songs