grebe vs podicipitiform seabird

grebe and podicipitiform seabird both are nouns.

Word	Noun	Adjective	Verb	Adverb
grebe	Yes	No	No	No
podicipitiform seabird	Yes	No	No	No

As nouns, podicipitiform seabird is a hypernym of grebe; that is, podicipitiform seabird is a word with a broader meaning than grebe:

grebe: small compact-bodied almost completely aquatic bird that builds floating nests; similar to loons but smaller and with lobate rather than webbed feet
podicipitiform seabird: aquatic birds related to the loons

grebe (noun)	podicipitiform seabird (noun)
small compact-bodied almost completely aquatic bird that builds floating nests; similar to loons but smaller and with lobate rather than webbed feet	aquatic birds related to the loons