Final answer:
The most beneficial adaptation for wading birds is waterproof feathers, as they enable the birds to stay dry and regulate body temperature while wading through water environments.
Step-by-step explanation:
Among the adaptations that wading birds have developed, waterproof feathers would be the most beneficial. This adaptation enables birds to stay dry and maintain their body temperature while wading through water, which is a common activity in their habitat. In contrast, light legs would be less essential since having lightweight legs does not confer an immediate survival advantage in aquatic environments.
Other adaptations seen in birds include beaks that are specialized for different food sources and feet that vary depending on their environment. For instance, waterfowl may have webbed feet for swimming, whereas birds like herons have long toes to walk through wetlands without sinking. Wading birds also benefit greatly from lightweight bodies that facilitate easier movement through the water without excessive energy expenditure.