bird food vs birdseed

bird food and birdseed both are nouns.

Word	Noun	Adjective	Verb	Adverb
bird food	Yes	No	No	No
birdseed	Yes	No	No	No

As nouns, bird food and birdseed are synonyms defined as:

Other synonyms of bird food include bird feed.

bird food (noun)	birdseed (noun)
food given to birds; usually mixed seeds	food given to birds; usually mixed seeds