Predation on the urchin Echinometra lucunter (Linnaeus) by migratory shorebirds on a tropical reef flat

Predation on urchins by migratory shorebirds was investigated during tidal exposure of the reef flat at Galeta, Panama. Avian predators, primarily ruddy turnstones Arenaria interpres (Linnaeus) reduced the patchiness of Echinometra lucunter (Linnaeus), the most abundant urchin on the reef flat. No mortality of E. lucunter occurred in quadrats protected from avian predation. No mortality occurred when urchin crowding was increased experimentally in protected areas. Stress-induced mortality could not be determined from the condition of tests alone, since turnstones were capable of removing lantern and internal organs without damage to the test. The importance of shorebird predation in reef communities during aerial exposure can be hard to detect because mortality can occur during brief periods, at night, and without damage to urchin tests.