It would be more helpful to have the whole sentence, however; if you were to say, "The hat that covered their hair," it would be recognized, not as an adverb, but as an adverbial phrase.
Yes, the moose is covered with hair (fur).
The adverb of sweet is sweetly.An example sentence is: "he sweetly complimented her hair".
Yes they actually are they are covered in fur pink or brown depends if they are in mud.
Hair.
Yes, Punjabi's must have their hair or head covered but only if they are Punjabi women.
The hare is covered in hair?
The adverb of the word "vain" is vainly.An example sentence is: "she vainly checks her hair again".
None of those words is an adverb. It could be a predicate: verb/adjective/noun.
Mammals are not covered with feathers. Mammals grow hair, but do not have to be covered with hair. Birds are covered with feathers.
fur/hair
Hair.
An Echidnas body is covered with hair to keep them warm