howler vs blooper

howler and blooper both are nouns.

Word	Noun	Adjective	Verb	Adverb
howler	Yes	No	No	No
blooper	Yes	No	No	No

As nouns, blooper is a hypernym of howler; that is, blooper is a word with a broader meaning than howler:

Other hypernyms of howler include bloomer, blunder, boner, boo-boo, botch, bungle, flub, foul-up, fuckup, pratfall.

howler (noun)	blooper (noun)
a glaring blunder	an embarrassing mistake
monkey of tropical South American forests having a loud howling cry
a joke that seems extremely funny