Rockhopper penguin positions and islands became surrounded by subtropical water masses, resulting in a split between Northern and Southern rockhopper penguins. Many advance and retreat cycles of Patagonian icecaps during the late Pleistocene may have created a barrier to gene flow between Southern Pacific and Southern Atlantic populations, causing a split between Southern and Eastern rockhopper populations. Adult Rockhopper penguins have no land-based predators. They are eaten when at sea by leopard seals, fur seals, killer whales and blue sharks. Chicks and eggs are eaten by many birds including giant petrels, skuas, sheathbills and various types of gulls. Although the rockhopper penguin
What Bird is That? friends, together with the succinct but compendious descriptive information, will place within easy reach of the bird lover, a most valuable "vade mecum" of bird and bush lore for out of doors as well as a thing of beauty for the library." Cayley’s aim in creating this work was to make available a book that would encourage and help people to learn about and appreciate Australia’s remarkable and unique bird life. He saw and responded to a need for a simple book that was accessible to the non-specialist birdwatcher. Each species was illustrated in colour and the birds were organised