"I bet it sneaked up here from Experimental Charms, they're so careless, remember that poisonous duck?"
-- young female pamphlet-maker (DH13)
Ducks which can poison someone.
The Committee on Experimental Charms had at least one poisonous duck in its offices in the Ministry of Magic headquarters. Due to carelessness, a poisonous duck made its way from Experimental Charms to Level One (DH13).
Technically, an animal is poisonous if you ingest it and it causes you harm, while a venomous animal is one that bites, stings, or otherwise actively injects a harmful substance into an enemy (source: Smithsonian.com). It may be that Rowling mixed these words up just like the rest of us and meant that these ducks produce a harmful chemical when they bite or it could be that these ducks are harmless unless eaten. -BB