gray whale vs whalebone whale

gray whale and whalebone whale both are nouns.

Word	Noun	Adjective	Verb	Adverb
gray whale	Yes	No	No	No
whalebone whale	Yes	No	No	No

As nouns, whalebone whale is a hypernym of gray whale; that is, whalebone whale is a word with a broader meaning than gray whale:

gray whale: medium-sized greyish-black whale of the northern Pacific
whalebone whale: whale with plates of whalebone along the upper jaw for filtering plankton from the water

Other hypernyms of gray whale include baleen whale.

gray whale (noun)	whalebone whale (noun)
medium-sized greyish-black whale of the northern Pacific	whale with plates of whalebone along the upper jaw for filtering plankton from the water