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? to the League for £300. The book was extolled fulsomely by S.R. Thomas, of the NSW Department of Education, as follows; ""What Bird is That?" is the most comprehensive and informative bird book published in the Commonwealth – if not in the world. The coloured plates are a triumph not only of the genius and imagination of the artist – our own Neville Cayley on whom has fallen so fittingly the mantle of his famous father – but also of the block-maker’s and printer’s art. The publishers have done nothing finer of its kind. The life-like portrayals of our feathered