bird feeder vs birdfeeder

bird feeder and birdfeeder both are nouns.

Word	Noun	Adjective	Verb	Adverb
bird feeder	Yes	No	No	No
birdfeeder	Yes	No	No	No

As nouns, bird feeder and birdfeeder are synonyms defined as:

bird feeder and birdfeeder: an outdoor device that supplies food for wild birds

Other synonyms of bird feeder include feeder.

bird feeder (noun)	birdfeeder (noun)
an outdoor device that supplies food for wild birds	an outdoor device that supplies food for wild birds