marsh hen vs swamphen

marsh hen and swamphen both are nouns.

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

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

marsh hen and swamphen: 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 gallinule, water hen.

marsh hen (noun)	swamphen (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