purple gallinule vs gallinule

purple gallinule and gallinule both are nouns.

Word	Noun	Adjective	Verb	Adverb
purple gallinule	Yes	No	No	No
gallinule	Yes	No	No	No

As nouns, gallinule is a hypernym of purple gallinule; that is, gallinule is a word with a broader meaning than purple gallinule:

purple gallinule: gallinules with showy purplish plumage
gallinule: any of various small aquatic birds of the genus Gallinula distinguished from rails by a frontal shield and a resemblance to domestic hens

Other hypernyms of purple gallinule include marsh hen, swamphen, water hen.

purple gallinule (noun)	gallinule (noun)
gallinules with showy purplish plumage	any of various small aquatic birds of the genus Gallinula distinguished from rails by a frontal shield and a resemblance to domestic hens