There are three gannet species worldwide, all with adults similar in appearance. The northern gannet (Morus bassanus) is a North Atlantic bird which does not venture into southern waters. The African Cape gannet (Morus capensis) appears infrequently in Australian and New Zealand waters. It is recognised by the long black stripe on its throat and a completely black tail. The Australasian gannet (Morus serrator) is found in Australian and New Zealand waters.
Fake it till you make it
In 2008 decoy gannets made of concrete were used to entice Australasian gannets to breed in a pest-free enclosure on Young Nick's Heard, near Gisborne. An audio system played gannet colony sounds as further encouragement. The experiment was a success, with birds returning year after year and fledging chicks.
With its 2-metre wingspan, golden head and dramatic plunging dives, the white Australasian gannet is an easily identified seabird. Adult gannets are about the size of a goose, with black-tipped wings, black central tail feathers and a strong, conical blue-grey beak. Juvenile birds look quite different. In their first year they have speckled brown feathers on their upper body, and white undersides. Each year more white feathers appear on their backs, and the birds acquire their adult appearance by five years of age.
Australasian gannet numbers in New Zealand increased markedly during the second half of the 20th century – from an estimated 27,000 breeding pairs in the first census of 1947, to 46,000 in the 1980–81 count. New Zealand is home to 87% of the total population of adult birds.
Māori made expeditions to the rocky breeding grounds of gannets, or tākapu, catching the young birds for food and the adults for their bones and plumage. Bones were fashioned into chiselling tools and used for applying elaborate facial moko (tattoos). The valuable white feathers were used to decorate canoes, or were worn by high-ranking individuals.
New Zealand is one of the best places in the world to view Australasian gannets. There are three accessible mainland breeding colonies – at Cape Kidnappers, Muriwai and Farewell Spit.
There are also 21 offshore gannetries, and an expanding population. The largest breeding colonies are on the Three Kings Islands, Gannet Island, and White Island. The birds live all around New Zealand’s coastal waters, especially north of Cook Strait. They are also found around much of the Australian coast, including Lord Howe and Norfolk islands.
Gannets usually breed in colonies on offshore islands. However, in 1880 a New Zealand naturalist, Henry Hill, noted that about 50 gannets had started breeding on an elevated headland at Cape Kidnappers in Hawke’s Bay. The area was protected as a reserve in 1915 and the gannet population steadily increased. By the late 1990s there were 6,500 breeding pairs in four sub-colonies. For nearly a century Cape Kidnappers remained the only mainland colony in New Zealand.
In the 1980s a colony established itself north of Auckland at Muriwai Beach. Two headlands were fenced off to protect nesting gannets that had arrived from nearby Motutara Island. However, the fences eventually prevented the colony from expanding. Once they were removed, in 1996–97, the population more than doubled within four years.
Unlike the Cape Kidnappers and Muriwai colonies, which are on elevated sites, the most recently established colony is practically at sea level. The birds breed on shell banks at Farewell Spit, at the north-west tip of the South Island. Beginning with 75 breeding pairs in 1983, the colony grew to around 600 pairs by 1987. The site is vulnerable to storms; the colony was nearly wiped out in January 1997 by Cyclone Drena, but eventually recovered.