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 inference is supported by the observation that fewer nests were noted in dry years compared to wet years, suggesting that the availability of food, which is influenced by water depth, plays a significant role in reproductive success for wading birds.