Holden’s fixation on the ducks in the Central Park lagoon represents his fear of change. When he worries about where the ducks go during the wintertime, he finds himself unsettled by the idea that they have to alter their lives in order to survive. What he fails to realize, though, is that they aren’t altering their lives, since seeking out warmer environments is simply part of their migration pattern and, thus, doesn’t represent any kind of change for them. In fact, that the ducks always return to the lagoon in warmer weather should actually comfort Holden, since it suggests that certain things really do stay the same even if change is an inherent part of life. Nevertheless, Holden is too concentrated on the idea that the ducks have to adapt in order to stay alive, so he remains unable to see the flaws in his thinking. In turn, the ducks become an embodiment of the tunnel-vision Holden gets when he starts to obsess about change and the future.
The timeline below shows where the symbol The Ducks in the Lagoon in Central Park appears in The Catcher in the Rye. The colored dots and icons indicate which themes are associated with that appearance.
...Ernie’s, Holden strikes up a conversation with his cab driver, Horwitz. When he asks about the ducks in the Central Park lagoon, Horwitz becomes angry at the stupidity of his question, shouting... (full context)