bastard wing vs alula

bastard wing and alula both are nouns.

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

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

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

Other synonyms of bastard wing include spurious wing.

bastard wing (noun)	alula (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
	scalelike structure between the base of the wing and the halter of a two-winged fly