bird nest vs nest

bird nest and nest both are nouns.

Word	Noun	Adjective	Verb	Adverb
bird nest	Yes	No	No	No
nest	Yes	No	Yes	No

As nouns, nest is a hypernym of bird nest; that is, nest is a word with a broader meaning than bird nest:

bird nest (noun)	nest (noun)
nest where birds lay their eggs and hatch their young	a kind of gun emplacement
	furniture pieces made to fit close together
	a gang of people (criminals or spies or terrorists) assembled in one locality
	a cosy or secluded retreat
	a structure in which animals lay eggs or give birth to their young

bird nest (verb)	nest (verb)
	fit together or fit inside
	gather nests
	move or arrange oneself in a comfortable and cozy position
	inhabit a nest, usually after building