In J.D. Salinger's "The Catcher in the Rye," the ducks that Holden Caulfield is concerned about throughout the book are a symbol of his own anxiety and fear of change. The ducks represent Holden's feeling of being lost and his fear of not being able to adapt to the changing world around him. He worries about where the ducks go during the winter when the pond freezes over, just as he worries about his own uncertain future.
Holden's fixation on the ducks is also a manifestation of his desire to save others from the harsh realities of the world. He wants to be the "catcher in the rye," a figure who saves children from falling off the edge of a cliff and into the adult world. This desire stems from his own trauma and pain, and his inability to come to terms with the loss of his younger brother Allie.
Furthermore, the ducks can be interpreted as a metaphor for the novel's central theme of innocence and the loss of innocence. The ducks are a symbol of the fleeting innocence that is lost as one grows older and faces the challenges and responsibilities of adulthood. Holden, in his own way, is trying to hold onto his own innocence and protect others from losing theirs.
Overall, the ducks in "The Catcher in the Rye" are a powerful symbol that represents Holden's fear of change, his desire to save others from the harsh realities of the world, and the novel's central theme of innocence and the loss of innocence.