peck vs pick at

peck is a noun but pick at is not a noun.

Word	Noun	Adjective	Verb	Adverb
peck	Yes	No	Yes	No
pick at	No	No	Yes	No

As verbs, peck and pick at are synonyms defined as:

Other synonyms of peck include peck at.

peck (noun)	pick at (noun)
a light kiss
bite by a bird
(often followed by `of') a large number or amount or extent
a United States dry measure equal to 8 quarts or 537.605 cubic inches
a British imperial capacity measure (liquid or dry) equal to 2 gallons

peck (verb)	pick at (verb)
bother persistently with trivial complaints	express a negative opinion of
eat by pecking at, like a bird	eat like a bird
eat like a bird	pluck or pull at with the fingers
kiss lightly
hit lightly with a picking motion