The seagull wing is an item on the Odd Old Man's wish list after the Rag and Bone Man quest. It is dropped by seagulls. After the quest is completed you can no longer obtain this as a drop. The bone must be put into a pot of vinegar and boiled to create a polished seagull wing before giving it to the Odd Old Man.
Monster Combat level Quantity Rarity Seagull 2 1 Common