nest vs birdnest

nest and birdnest both are nouns.

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

As nouns, birdnest is a hyponym of nest; that is, birdnest is a word with a more specific, narrower meaning than nest:

Other hyponyms of nest include beehive, hive, bird's nest, bird nest, drey, mouse's nest, mouse nest, nidus.

nest (noun)	birdnest (noun)
a kind of gun emplacement	nest where birds lay their eggs and hatch their young
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

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