Hauturu – Haven for birds

The Hauraki Gulf (Tikapa Moana) is known in the birding community as the seabird capital of the world, as it is home to so many species. It is not surprising to discover the importance of Te Hauturu-o-Toi to many of these seabirds, standing as it does as sentinel in the gulf. What perhaps is little realised is the importance of the seabirds to the island.

Their guano, or droppings, bring a rich source of nutrients to the island’s forest cover and all the creatures that thrive there. The seabirds’ burrowing during their nest building helps to till the soil and improve it. The run-off from seabird islands has been shown to enrich the near shore marine habitat, increasing the number of species of marine plants and animals.

Of the seabirds that breed on Hauturu, the migratory Cook’s petrel is the most common, with numbers into the hundreds of thousands. They spend the northern summer in the oceans off southern California, returning in the southern summer to burrow and breed in the forest of Hauturu. Every day during the breeding season, they announce their night time arrival and dawn departure with deafening chatter. The birds actually climb trees to launch themselves off for their day’s fishing and feeding in the gulf and beyond. Cook’s petrel would once have returned in their millions to breed on the mountain ranges of New Zealand’s mainland, but forest clearance and mammalian predators have reduced their breeding grounds to Hauturu and a very small sub-species population on Whenua Hou (Codfish Island) in Foveaux Strait.

The black petrel, which mainly breeds on Aotea/Great Barrier Island, has a small breeding population of several hundred birds on the high ridges of Hauturu. They, too, would once have been present on mainland ridge tops. Their evening return to the island is much quieter than the Cook’s petrel. In fact, the large birds appear against the night sky rather like stealth bombers!

The New Zealand storm petrel, once believed to be extinct and rediscovered in 2003, is only known to breed on Hauturu. So far, very little is known about these tiny birds. It would appear, now that Polynesian rats (kiore) have been removed from the island, that storm petrel numbers are increasing. There are now around 1000 birds.

There are several other species of seabirds known or believed to be breeding on Hauturu.

The grey-faced petrel is re-establishing breeding colonies on some of Hauturu’s cliff tops and also breeds on several other Gulf islands, as well as the cliffs of Tawharanui. The little blue penguin breed around the coast and sometimes well into the forest. Pied shag have a favourite breeding spot on the south coast. Fluttering shearwater, diving petrel, white-fronted terns and black-backed gull all breed either in the forest or on rocky cliffs and outcrops around the island. Possibly other species are returning now that cats and rats are gone.

The increasing human impact within the gulf means the seabirds have to compete with us to find sufficient food to feed themselves and their young, often having to travel hundreds of kilometres to gather food. A reduction in the availability of food for the seabirds and their young will be a limiting factor to the numbers and health of the birds in Tikapa Moana/Hauraki Gulf.

Lyn Wade, Little Barrier Island Supporters Trust
www.littlebarrierisland.org.nz