Step 1: Select Smart Carver from the Image menu.
Step 2: Using the green Preserve brush, mark the areas in the photograph that you want to keep as-is – that is, the areas that you don't want to be distorted. If, in addition, you have areas in the photo that you'd like to get rid of, go ahead and mark those with the red Remove brush as well.

click to enlarge
In this example, we wanted to leave the bird unchanged so it was marked with the
Preserve brush. There weren't any objects that we wanted to remove, so no red areas are marked.