bastard wing vs spurious wing

bastard wing and spurious wing both are nouns.

Word	Noun	Adjective	Verb	Adverb
bastard wing	Yes	No	No	No
spurious wing	Yes	No	No	No

As nouns, bastard wing and spurious wing are synonyms defined as:

bastard wing and spurious wing: tuft of small stiff feathers on the first digit of a bird's wing

Other synonyms of bastard wing include alula.

bastard wing (noun)	spurious wing (noun)
tuft of small stiff feathers on the first digit of a bird's wing	tuft of small stiff feathers on the first digit of a bird's wing