kittiwake vs seagull

kittiwake and seagull both are nouns.

Word	Noun	Adjective	Verb	Adverb
kittiwake	Yes	No	No	No
seagull	Yes	No	No	No

As nouns, seagull is a hypernym of kittiwake; that is, seagull is a word with a broader meaning than kittiwake:

kittiwake: small pearl-grey gull of northern regions; nests on cliffs and has a rudimentary hind toe
seagull: mostly white aquatic bird having long pointed wings and short legs

Other hypernyms of kittiwake include gull, sea gull.

kittiwake (noun)	seagull (noun)
small pearl-grey gull of northern regions; nests on cliffs and has a rudimentary hind toe	mostly white aquatic bird having long pointed wings and short legs