About 30 species of bird regularly nest on the island, including ravens, little owls, oystercatchers and the rare chough. Hundreds of sea birds, including razorbills, guillemots, fulmars and kittiwakes, spend the summer nesting on the island's eastern cliffs. There are no land predators such as rats or foxes on the island. On a dark moonless night an eerie cackling can be heard across the island as 7,000 pairs of Manx shearwaters, 3.5 per cent of the British population, come ashore to lay and incubate their eggs in abandoned rabbit warrens or newly dug burrows.