Storks simply aren’t able to defend their nests against raccoons, possums and other climbing mammals that may raid their nests.However, these mammals may be deterred by having to swim to the colony site, which may be why storks usually choose to nest over open water. In addition, storks may also be protected from mammals by the presence of alligators, which tend to hang around colonies hoping to pick up scraps of dropped food or chicks that fall out of nests.

Although mammals can cause real havoc in a stork colony, interruptions in the food sources are a more common cause of nest failure. Storks will abandon their nesting attempt, even when there are large young in the nest, if they have trouble getting food. Due to their specialized foraging technique and need for concentrated prey, storks are sensitive to changes in water level and temperature, both of which can cause prey to become more dispersed, or harder to find. 

This process may also explain why storks have had such a hard time nesting in south Florida since the 1970s. Between 1931 and 1946 in Everglades National Park, for example, about 90% of breeding colonies were successful.. Between 1974 and 1989, the same statistic had declined to 44%. During the latter period, water management practices had resulted in unseasonal changes in water level during the winter/spring nesting season, frequently disrupting the low surface water and drying patterns that storks need to feed and breed. The current Comprehensive Everglades Restoration Plan is aimed largely at restoring natural timing and flows of water to the Everglades.