The most reasonable inference about the relationship between wading bird reproductive success and water depth in the Everglades, based on the information provided, is:
Water depth likely affects wading birds’ access to food and thus affects wading birds’ reproductive success.
This conclusion is drawn from the observation that fewer nests were observed in dry years (which can be associated with lower water depths) compared to wet years, suggesting that changes in water levels may influence the availability of food (fish) for the wading birds, subsequently impacting their reproductive success.