green woodpecker vs peckerwood

green woodpecker and peckerwood both are nouns.

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

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

green woodpecker: woodpecker of Europe and western Asia
peckerwood: 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 pecker, woodpecker.

green woodpecker (noun)	peckerwood (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