louse vs bird louse

louse and bird louse both are nouns.

Word	Noun	Adjective	Verb	Adverb
louse	Yes	No	No	No
bird louse	Yes	No	No	No

As nouns, louse and bird louse are synonyms defined as:

louse and bird louse: wingless insect with mouth parts adapted for biting; mostly parasitic on birds

Other synonyms of louse include biting louse.

louse (noun)	bird louse (noun)
wingless usually flattened bloodsucking insect parasitic on warm-blooded animals	wingless insect with mouth parts adapted for biting; mostly parasitic on birds
any of several small insects especially aphids that feed by sucking the juices from plants
wingless insect with mouth parts adapted for biting; mostly parasitic on birds
a person who has a nasty or unethical character undeserving of respect