I didn’t want to start an argument. “Okay,” I said. Then I thought of something, all of a sudden. “Hey, listen,” I said. “You know those ducks in that lagoon right near Central Park South? That little lake? By any chance, do you happen to know where they go, the ducks, when it gets all frozen over? Do you happen to know, by any chance?” I realized it was only one chance in a million.
He turned around and looked at me like I was a madman. “What’re ya tryna do, bud?” he said. “Kid me?”
“No – I was just interested, that’s all.”
He didn’t say anything more, so I didn’t either. Until we came out of the park at Ninetieth Street. Then he said, “All right, buddy. Where to?”

J. D. Salinger

The Catcher in the Rye. Chapter 9. Holden asks the cab driver where the ducks go when the lake is frozen over. His fascination with the ducks represents his fear of change. He is terrified by the idea of change, perhaps because of the loss of his brother Allie. Feeling isolated and alone in a period of immense change in his life, Holden looks at the ducks as a reflection of his own life. They are a symbol of the need to adapt and change their environment in order to survive the winter cold.