Place balsamic vinegar in a small saucepan. Bring contents to a boil, stirring occasionally, then reduce heat and simmer for 15 to 18 minutes. This allows the balsamic to reduce and thicken.
While balsamic is simmering, cube the rotisserie chicken pieces and place spring greens in a salad bowl. Cut watermelon into small cubes.
Just before serving place 2 cups of watermelon on the greens, add chicken, feta cheese and sunflower seeds. Top with the desired amount of reduced balsamic vinegar.
