bird-scarer vs effigy

bird-scarer and effigy both are nouns.

Word	Noun	Adjective	Verb	Adverb
bird-scarer	Yes	No	No	No
effigy	Yes	No	No	No

As nouns, effigy is a hypernym of bird-scarer; that is, effigy is a word with a broader meaning than bird-scarer:

bird-scarer: an effigy in the shape of a man to frighten birds away from seeds
effigy: a representation of a person (especially in the form of sculpture)

Other hypernyms of bird-scarer include image, simulacrum.

bird-scarer (noun)	effigy (noun)
an effigy in the shape of a man to frighten birds away from seeds	a representation of a person (especially in the form of sculpture)