green woodpecker vs pecker

green woodpecker and pecker both are nouns.

Word	Noun	Adjective	Verb	Adverb
green woodpecker	Yes	No	No	No
pecker	Yes	No	No	No

As nouns, pecker is a hypernym of green woodpecker; that is, pecker is a word with a broader meaning than green woodpecker:

green woodpecker: woodpecker of Europe and western Asia
pecker: bird with strong claws and a stiff tail adapted for climbing and a hard chisel-like bill for boring into wood for insects

Other hypernyms of green woodpecker include peckerwood, woodpecker.

green woodpecker (noun)	pecker (noun)
woodpecker of Europe and western Asia	bird with strong claws and a stiff tail adapted for climbing and a hard chisel-like bill for boring into wood for insects
	horny projecting mouth of a bird
	obscene terms for penis