A brown noddy rests on the faecal-grey rocks of Egg Island, St Helena's premier seabird colony. These birds rarely nest on the main island due to invasive non-native predators including rats and cats. Egg Island remains predator free up to now despite nearly being connected to the mainland at low tide by a rocky isthmus. Egg Island contains ruins and old canons (which Madeiran storm petrels use for nesting burrows) of Cockburn's Battery dating back to the the 19th century Napoleonic defences.