Seabirds are birds that obtain all or nearly all of their food at sea. There are just 360 species of seabird out of a total of 9,000 bird species worldwide. Of this 360, 86 breed in the New Zealand region, including 38 (10% of the world total) which breed nowhere else. A further nine migratory species breed elsewhere but visit New Zealand each year, and a number of others are recorded in New Zealand waters from time to time. With a greater diversity of seabirds than anywhere else, New Zealand can rightfully claim to be the world's seabird capital. New Zealand’s seabirds include penguins, albatrosses, petrels, shags, gannets, terns and skuas.
A few seabird species in New Zealand are amazingly abundant. The most numerous is probably the sooty shearwater (Puffinus griseus), more commonly known as the muttonbird (tītī). No systematic count has ever been made; however, in the 1970s it was estimated that there were 2.75 million breeding pairs on the Snares Islands, 100 kilometres south of Stewart Island. Including non-breeding birds and chicks, the total came to more than 7.5 million. To put this into context, there are only 3 million breeding pairs of seabirds in the entire British Isles. Sooty shearwater numbers may have declined by up to 37% since this estimate, but even so they remain the most populous bird in the country – far more numerous than the sparrows (Passer domesticus) and starlings (Sturnus vulgaris) New Zealanders see every day. Fairy prions (Pachyptila turtur) and white-faced storm petrels (Pelagodroma marina) are also exceedingly plentiful on certain offshore islands that are free of rats.
A favourable environment
This abundance and diversity is a result of New Zealand’s rich marine environment. The New Zealand region extends from the subtropical waters around the Kermadec Islands to the cool, subantarctic waters of the Campbell Plateau. The subtropical convergence, where the so-called subtropical waters and subantarctic waters meet, extends around the southern shores of the South Island and east to the Chatham Islands. These conditions combined with the topography of submarine landforms create areas of upwelling where nutrients, fish and seabirds are abundant. One such area is along the Kaikōura coast. A diversity of marine life exists here because the sea floor goes abruptly from shallow to deep, creating a range of different habitats within a small area.