Editorial
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by Emma Waterhouse
I've just returned from the Glenfern Walk in Port FitzRoy and was lucky enough to spy a black petrel chick in its burrow under an old gnarled puriri tree. What a treat, although I suspect the chick did not share my enthusiasm! Glenfern Sanctuary is now an Auckland Council regional park, under the management of a newly formed trust, charged with developing and enhancing the sanctuary for conservation, education and recreation.
It’s great to see Glenfern ‘open for business’ once again. The low predator numbers in the Glenfern Sanctuary (and wider Kotuku Peninsula Sanctuary) are a major reason black petrel (and Cook’s petrel) have bred there in recent years. Although these seabirds may well have nests in other isolated parts of the island, Hirakimata/Mt Hobson remains as the main breeding population for black petrel, New Zealand’s most ’at risk’ seabird.
A real and relatively immediate possibility exists for a second viable population on Aotea/Great Barrier to become established—this time on Rakitu off the island’s east coast. For over a decade there has been talk of eradicating rats and other predators off Rakitu (see timeline on page 20), yet action on the ground continues to be sadly lacking.
The island sits at a mid point on the North Island’s east coast ’seabird superhighway’ (see page 4), a chain of predator-free islands that stretch from the Three Kings Islands to the Bay of Plenty (see map at right). It’s no coincidence that these islands host breeding colonies of over 25 species of seabird, a true biodiversity hotspot, with more pest-controlled mainland areas such as Bream Head, and recently pest-free islands like the Mercury group likely candidates for colonies to become established in the future.
Seabird colonies along the east coast of the northern North Island. Most of these colonies occur on islands free of predators or in predator controlled areas, like Glenfern Sanctuary on Aotea/Great Barrier. A predator-free Rakitu would provide another (obvious) link in this island chain, described by ornithologists as a ‘seabird super highway’.
Figure credit: H. Unkovich & E. Waterhouse
It’s not hard to see that Rakitu is ideally placed on the seabird highway, and expert opinion suggests that at least six species would become established there following the removal of rats (and weka). Just look at the rapid colonisation of Burgess Island in the Mokahinau group (see page 7), with seven species of burrowing seabirds now present following pest eradication, and with little, if any, active management. This model of ‘passive restoration’ could also work on Rakitu, but not if the current population of weka remain. Alternatives exist to relocate these birds elsewhere (see page 9). The stock of islands that could host breeding populations of our most vulnerable seabirds is, in contrast, severely limited.
While some progress is being made, the planned rat eradication is likely to be delayed yet again, until 2018. And we understand that the weka are to remain. Why? Weka equals no seabirds, which, we assume, was one of the groups of species identified as a major beneficiary of the eradication in the first place!
The cliffs and forests of Rakitu once rang out with the calls of thousands of seabirds—and they can once again. But the Department of Conservation needs to get the job done now, using the available funding.
Cuvier Island (left) and Mercury Islands (in the distance) from Kaitoke. Like Aotea/Great Barrier, both sit squarely on the seabird super highway—but unlike Aotea, are pest-free. Rakitu, off Aotea’s east coast, has been earmarked for rat eradication for over a decade. With the removal of rats (and weka), the island could provide another important link in the chain of seabird islands along the North Island’s east coast. Photo: E. Waterhouse
Recent research for the Hauraki Gulf and elsewhere clearly demonstrates that support for pest eradication and ongoing management is closely related to a community’s first hand experience of such programs, and very importantly, the outcomes they bring. So as the Rakitu story plays out, what we do know is that there must be clear objectives for management of the island following the eradication, including how iwi and the Aotea/Great Barrier and wider community, are to be involved. These groups all have an interest and stake in the future of Rakitu.
Meanwhile on the Aotea mainland, the Trust has been active in managing a rat monitoring program on Hirakamata. Volunteer support has been critical to this effort which has so far returned some interesting results (see page 18). Rats are a serious threat to birdlife and seem to have well and truly adapted to mountain life! Monitoring is continuing.
We hope you enjoy reading this newsletter and gratefully acknowledge the support of the Great Barrier Local Board with funding to produce our first full colour Environmental News.
Environmental News Issue 37 Autumn 2017