Clapper Rail (Rallus longirostris) carefully crossing BEHIND the Great Blue Heron (Ardea herodias). Some people say that these open channels in the marshes on South Padre are made by humans flipping sheets of plywood. Other favor the theory that they are created by alligators. My theory is that they are created by herds of rails, reptiles, amphibians, and small mammals stampeding behind passing Great Blue Herons.