The answer is that the population will eventually level off. This is because, as the fish increase, the wading birds will increase bountiful of food for them. Consequently, there will be more wading birds feeding on the fish hence more predation will result to decrease until the numbers of fish cannot support the large wading birds population. Due to stiff competition, the wading birds numbers will decrease. This is the leveling off implied.
The relationship between the fish and the wading bird is a predator-prey relationship. A change in the size of one population affects all other organisms within the ecosystem. It is referred to as a "+/-" interaction since one benefits and the other loses. Predators and their prey evolve together. Over time, prey animals develop adaptations to help them avoid being eaten and predators develop strategies to make them more effective at catching their prey.