migrator vs leaver

migrator and leaver both are nouns.

Word	Noun	Adjective	Verb	Adverb
migrator	Yes	No	No	No
leaver	Yes	No	No	No

As nouns, leaver is a hyponym of migrator; that is, leaver is a word with a more specific, narrower meaning than migrator:

Other hyponyms of migrator include departer, goer, emigrant, emigre, emigree, outgoer, evacuee, immigrant, rusher, colonist, settler.

migrator (noun)	leaver (noun)
an animal (especially birds and fish) that travels between different habitats at particular times of the year	someone who leaves
traveler who moves from one region or country to another