birdbrain vs addle-head

birdbrain and addle-head both are nouns.

Word	Noun	Adjective	Verb	Adverb
birdbrain	Yes	No	No	No
addle-head	Yes	No	No	No

As nouns, birdbrain and addle-head are synonyms defined as:

birdbrain and addle-head: a person with confused ideas; incapable of serious thought

Other synonyms of birdbrain include addlehead, loon.

birdbrain (noun)	addle-head (noun)
a person with confused ideas; incapable of serious thought	a person with confused ideas; incapable of serious thought