Te Papa vertebrate curator Dr Colin Miskelly recently led a team that visited Takapourewa / Stephens Island Nature Reserve, to select and gather up 100 fairy prion chicks to move to Mana Island near Wellington. This is the fifth in a series of blogs about the project and the wildlife of Takapourewa.
Entering the forest on Takapourewa during the daytime is akin to entering a ghost town. The forest is almost devoid of those bird species typically found on islands free of introduced predators. And the numerous burrows and musty odour hint at owners no longer present – with mute tuatara scattered throughout as sepulchral sentinels. To those who know the island’s tragic recent history, the silence is deeper, holding memories of species no longer with us.
Little more than 120 years ago, Takapourewa was alive with a remarkable fauna, providing a window into ancestral Aotearoa before human contact. The forest teemed with at least 12 bird species that are no longer present (and at least two of which are globally extinct). The most famous (or infamous) loss was Lyall’s wren (also known as the Stephens Island wren), which was extinct within a year of its discovery. The extinction of all these species on Takapourewa occurred within a few short years of the decision being made to construct a lighthouse on the island, and was caused by the combined impacts of forest clearance and the introduction of cats (as companion animals for the lighthouse-keeping families). The cats were eradicated by 1925, but this was three decades too late for the birds.
The forest does still hold common species such as silvereye, fantail and grey warbler. However, there are no banded rails, pigeons, parrots, saddlebacks, yellowheads, brown creepers, bellbirds, tui, robins, tomtits or fernbirds, let alone wrens, kokako or piopio.
While the landbirds of Takapourewa are a sad shadow of their former glory, the seabirds remain spectacular. During our visit in mid-January, the lower slopes of the island echoed with the clamour of nesting red-billed gulls, black-backed gulls and white-fronted terns, three species of shag were seen around the coast, and variable oystercatchers nested on the only accessible beach.
However, it was as night fell that the true importance of the island for seabirds was revealed. Five species of burrow-nesting seabirds breed on Takapourewa, all of which return to the island only under the cover of darkness. The first to appear are sooty shearwaters, swooping low over the summit ridge while there is still just enough light to make out their dark silhouettes. About the same time, little penguins emerge from the sea to start their long, slow climb up the steep coastal slopes.
As true dark descends, the rotating beams of the lighthouse illuminate a blizzard of pale bodies as thousands, nay millions of fairy prions descend on the island. The island is honeycombed with burrows, of which 1.83 million are estimated to belong to the prions, along with smaller populations of sooty shearwaters, fluttering shearwaters and common diving petrels. We did not hear diving petrels during our visit (the chicks fledge in November and December). However, the fluttering shearwaters that we heard each night would have had chicks that were close to full grown, and the sooty shearwaters were caring for fluff-balls that would not depart the island for another 3-4 months.
The reason why these seabirds all use the cloak of darkness to visit their nests was readily apparent from their plucked remains scattered around the island. The vast seabird colonies supported two species of bird-hunting raptors. The 3-4 swamp harriers present quartered the southern half of the island, searching for dead or dying fairy prions caught in the open during the day. But they dared not venture north for fear of being driven back by aggressive territorial attacks from a pair of New Zealand falcons and their two one-year-old offspring. The falcons were also feeding on the prions, with the thousands of fully-grown and departing chicks proving easy prey.
The only mammals (other than a few humans) now present on Takapourewa are New Zealand fur seals that breed around the rocky shoreline. These have recolonised central and northern New Zealand since the last open season in 1946, revealing the impact that Maori hunting had on their populations. By the time European sealers reached our shores in the 1790s, commercial harvest of fur seal skins was possible only as far north as southern Westland. While some subantarctic fur seal colonies have yet to recover from near extirpation by sealing gangs 200 years ago, there are now more seals in Cook Strait than Cook himself encountered.
For a full list of bird species that regularly occur on Takapourewa, click here
For a full list of bird species that occasionally reach Takapourewa, click here
For a full list of bird species that formerly occurred on Takapourewa, click here