The duck in Ibsen's The Wild Duck is a complex symbol. This is the first play in which Henrik Ibsen used a newly innovated style of symbolism. It took critics and audiences a few years to catch on to what Ibsen was doing with his new symbolism and characterizations. He had made his name as a great playwright through plays about social problems. The Doll's House is one of his most famous social issue plays. His new symbolism was at a level of complexity that it took some getting used to.
The duck symbolizes both captivity and freedom. It symbolizes captivity to a physical place, to a idea, to a way of being, to circumstances, to bad choices, etc., because it is living in captivity after being shot by Hakon. It symbolizes freedom because as a wild duck it must be free and because it has a natural symbolism of nature and freedom inherent in its identity as a duck and some characters, like Old Ekdal idealize it for that reason. This brings up another level of the duck's symbolism. Different characters associate the duck with different ideas. To Old Ekdal the duck symbolizes his earlier life in which he was happy. To Hedvig the duck symbolizes the lie that is destroying her family. To Hjalmar the duck symbolizes an escape, a distraction from his present circumstances of life.