bird-nest vs birdnest

bird-nest is not a noun while birdnest is a noun.

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

As verbs, bird-nest and birdnest are synonyms defined as:

bird-nest (noun)	birdnest (noun)
	nest where birds lay their eggs and hatch their young

bird-nest (verb)	birdnest (verb)
gather birdnests	gather birdnests