song thrush vs thrush

song thrush and thrush both are nouns.

Word	Noun	Adjective	Verb	Adverb
song thrush	Yes	No	No	No
thrush	Yes	No	No	No

As nouns, thrush is a hypernym of song thrush; that is, thrush is a word with a broader meaning than song thrush:

song thrush: common Old World thrush noted for its song
thrush: songbirds characteristically having brownish upper plumage with a spotted breast

song thrush (noun)	thrush (noun)
common Old World thrush noted for its song	songbirds characteristically having brownish upper plumage with a spotted breast
	a woman who sings popular songs
	candidiasis of the oral cavity; seen mostly in infants or debilitated adults