longlegs vs shore bird

longlegs and shore bird both are nouns.

Word	Noun	Adjective	Verb	Adverb
longlegs	Yes	No	No	No
shore bird	Yes	No	No	No

As nouns, shore bird is a hypernym of longlegs; that is, shore bird is a word with a broader meaning than longlegs:

longlegs: long-legged three-toed black-and-white wading bird of inland ponds and marshes or brackish lagoons
shore bird: any of numerous wading birds that frequent mostly seashores and estuaries

Other hypernyms of longlegs include limicoline bird, shorebird.

longlegs (noun)	shore bird (noun)
long-legged three-toed black-and-white wading bird of inland ponds and marshes or brackish lagoons	any of numerous wading birds that frequent mostly seashores and estuaries