marsh hen vs gallinule

marsh hen and gallinule both are nouns.

Word	Noun	Adjective	Verb	Adverb
marsh hen	Yes	No	No	No
gallinule	Yes	No	No	No

As nouns, marsh hen and gallinule are synonyms defined as:

marsh hen and 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 synonyms of marsh hen include swamphen, water hen.

marsh hen (noun)	gallinule (noun)
any of various small aquatic birds of the genus Gallinula distinguished from rails by a frontal shield and a resemblance to domestic hens	any of various small aquatic birds of the genus Gallinula distinguished from rails by a frontal shield and a resemblance to domestic hens
a coot found in North America