Southern Ocean – fairly uniform temperatures of the deep ocean at the poles and the equator which differ by no more than 5 °C, and the major current systems or marine conveyor belt which transport egg and larva stages. The rocky shores of mainland Antarctica and its offshore islands provide nesting space for over 100 million birds every spring. These nesters include species of albatrosses, petrels, skuas, gulls and terns. The insectivorous South Georgia pipit is endemic to South Georgia and some smaller surrounding islands. Freshwater ducks inhabit South Georgia and the Kerguelen Islands. The flightless penguins are all located in the
Birds of New Zealand hedgehogs, and Australian possums also put pressure upon native bird species. The flightless birds were especially sensitive. Consequently, many bird species became extinct, and others remain critically endangered. Several species are now confined only to offshore islands, or to fenced "ecological islands" from which predators have been eliminated. New Zealand is today a world leader in the techniques required to bring severely endangered species back from the brink of extinction. Many bird species were introduced during the early years of European settlement to control insects as New Zealand birds species generally preferred a native bush habitat rather than the open