Breaksea Island/Te Au Moana in Fiordland is an iconic site for New Zealand conservation. It was one of the first large islands to be cleared of rats, when a team led by Rowley Taylor and Bruce Thomas (of Landcare Research) eradicated Norway rats in 1988.
This ambitious project followed the successful eradication of rats on much smaller (9 hectares) nearby Hawea Island in 1986.
But how has the wildlife on these islands responded to more than 30 years without rats? Vertebrates Curator Colin Miskelly reports on a recent field trip to find out.
170 islands and counting
Since 2016, Te Papa and the Department of Conservation have undertaken three expeditions to survey seabirds and land birds on the smaller islands in southern Fiordland.
The most recent survey, of Te Puaitaha / Breaksea Sound and Tamatea / Dusky Sound, was in December 2019, when 53 islands were searched, bringing the total to more than 170 islands.
The 2019 Breaksea Sound survey differed from the previous two surveys (of islands in Dusky Sound, Chalky Inlet, and Preservation Inlet) because we had good information on the birds that were present before rats were eradicated from Breaksea and Hawea Islands, and stoats prevented from recolonising numerous other islands closer to shore.
A bygone era
Much of this baseline information on bird populations on islands in Breaksea Sound was gathered during 1974 to 1986, before the Department of Conservation and Landcare Research were created as part of the major restructuring of science and government departments under the fourth Labour Government (1984–90).
Before these changes, Taylor and Thomas worked for Ecology Division of DSIR, and they were assisted by Lands & Survey Department rangers Kim Morrison and Ron Peacock from Fiordland National Park.
Recollections of islands teeming with rats
Among the team who cleared Hawea Island rats was a youthful Graeme Taylor – now a senior scientist with the Department of Conservation, and a member of our team.
Graeme’s recollections of rat-infested islands more than 30 years earlier added depth and colour to the changes in the bird communities that we discovered.
Breaksea Island – a Specially Protected Area
In addition to being one of the first large islands to be cleared of rats, Breaksea Island was a pioneer site for translocations of rare birds.
Tieke (South Island saddlebacks) from Big Island and Kundy Island (west of Stewart Island) were released there in 1992, and mohua (yellowheads) from the Blue Mountains, West Otago, were released there in 1995.
South Island robins (kakaruai) survived naturally on Breaksea Island, and these three species along with bellbirds are now the most abundant forest bird species on Breaksea Island.
The island has subsequently been the source of robins released on Anchor Island, Pigeon Island, and Indian Island, tieke released on South Passage Island, Anchor Island, Chalky Island, and to Orokonui Ecosanctuary, and mohua released on Chalky Island, Anchor Island, Pigeon Island, Whenua Hou/Codfish Island and to the South Branch, Hurunui River.
Robins are stronger fliers than tieke and mohua, and have colonised several islands up to 4 km from Breaksea Island since stoats were removed from Resolution Island and surrounding islands in 2008.
They are now common on the inner Gilbert Islands and Entry Island, and have apparently out-competed other insectivorous bird species (including tomtit and dunnock) that are now rare or absent on these islands.
This ‘trophic cascade’ effect has been documented at other restoration sites (e.g. Zealandia Sanctuary in Wellington), where removal of mammalian predators has allowed deep endemic bird species to flourish and to out-compete other bird species.
The main seabird species that we searched for was the bizarre-looking broad-billed prion.
This small burrow-nesting petrel was hugely abundant when Captain Cook and the naturalists accompanying him surveyed nearby Tamatea / Dusky Sound in 1773, but most of the Fiordland populations have been wiped out by introduced rats and stoats.
On top of this ongoing decline, a severe winter storm in 2011 killed more than 200,000 broad-billed prions, and we have little information on which breeding sites these birds were from.
During the 1980s, broad-billed prions were known to breed on two small islands in Breaksea Sound. We were able to confirm their presence at four additional sites, including on Breaksea Island itself, as the birds start to recover from more than 200 years of predation by rats and 100 years of stoat presence on some of the islands.
Fur seal recovery
One species that has had a spectacular recovery in Fiordland is the New Zealand fur seal, that was last hunted in 1946.
They were scarce on the islands in Breaksea Sound in the 1980s, but are now numerous enough on some islands to complicate our survey efforts.
December is the peak of their breeding season, with bulls aggressively defending their harems and breeding territories.
At several sites it was a challenge to find a safe route from the shoreline to the vegetation where burrow-nesting seabirds could be breeding.
Department of Conservation guidelines are to stay at least 20 metres away from seals, which we were happy to comply with – if only the seals did too!
On three of the outer islands their breeding territories were contiguous around the shoreline and well into the island interior, and some breeding bulls would charge from more than 20 metres away to evict us from their territories.
Fortunately, I had come forewarned and prepared, with a Seal Deterrent Device (aka a golf umbrella).
Suddenly unfurling the brightly-coloured umbrella stopped most of the rapidly approaching seals in their tracks, but my companions were too busy laughing or retreating (rapidly) to get good images or video of the effectiveness of the SDD.
An abundance of weevils
In addition to surveying for birds, we also searched for evidence of lizards and two species of large flightless weevils.
Before 2016 there was only a single known natural population of flax weevils in Fiordland.
We found evidence of their presence on an additional 17 islands in Breaksea Sound in 2019, but it is unknown whether this represents a true recovery, or whether they were simply overlooked previously.
As previously, the Te Puaitaha / Breaksea Sound survey was reliant on superb logistic and boat support by the crew of the DOC vessel Southern Winds, and thanks also to our team member and author Peta Carey who generously supplied images for this blog.
Dusky Sound – rich in history and wildlife
Seabird discoveries in remote southern Fiordland
Further flax weevil finds from farthest Fiordland
Riders of the storm – thousands of seabirds perish on New Zealand shores
This is wonderful news and so encouraging to see such efforts being rewarded by the return of wildlife.
Brilliant Seal Deterrent Device. Wish I’d been there to see it in operation!
Great blog Colin, thanks for your expertise and for sharing. A big thankyou to your amazing team including Peta, Te Papa and DOC staff for this follow up survey- awesome to see recovery occurring. Combined with the other recent Te Papa/DOC surveys our understanding of seabirds in Fiordland is much improved. Given the significance of seabirds at an ecosystem level they have a very low profile in NZ conservation. We are lucky to have a special group of knowledgeable enthusiasts. Keep up the great work.
Kia ora Lindsay
Thank you very much for your feedback – and thank you also for your support for the 2016 & 2017 surveys. Great to know that you are still keeping a close eye on what is happening in that special corner of Aotearoa.
Ngā mihi nui
Oh Colin, thank you! I was pregnant when I first visited Breaksea Island in 1981, with my parents and also Bruce Thomas. I will never forget the sperm whale skeleton laid out on the boulders of the leeward bay, nor of sitting in the bush with my Dad calling up a SI robin family, who sat on a branch above us and held a conversation with their youngsters about the flightless birds below. The plan to trap these islands was nutted out on board at night, along with the relationships between Fiordland black skinks, rats and fur seals. Bruce was also interested in the weevil living on the native carrot-related plant (sorry – I am a health scientist…). I learned SO much about my country on that trip and was so grateful for the opportunity given to me. When my son was 16 we travelled again to Fiordland on the Breaksea Girl, again with Bruce. It was a time of sadness, as the mustelids had arrived in force and many of the birds had gone. So your blog fills me with joy and hope for the future, especially the news of the broad-billed prion. Like Denis Asher, I want more!! Thank you, all of you, for your dedication and hard work, out there in all weathers, observing, trapping and monitoring and saving NZ’s taonga.
Kia ora Jean
Thank you very much for these wonderful recollections. I was aware that your father (Sir Charles Fleming) advocated for Breaksea Island to be cleared of rats, and it is now part of New Zealand conservation history that Rowley Taylor and Bruce Thomas picked up the ball and ran with it.
The weevil on the native carrot-related plant is the knobbled weevil (Hadramphus stilbocarpae) on Anisotome lyallii. We were looking for their feeding sign wherever we encountered Anisotome, and were surprised not to note any evidence of the weevils’ presence. However, our survey effort for these weevils was minimal – they are best searched for at night when they emerge to feed. Unfortunately Anisotome lyallii has a similar distribution to breeding fur seals, on the exposed outer islands of Fiordland (note the plants with white flowers in the middle of the image showing fur seals on Wairaki Island, and to the right of the bull fur seal in the Seal Deterrent Device image). It would be foolhardy to land or move about on these islands at night during the peak of the seal breeding season.
In response to your comment about wanting more, please see my reply to Denis Asher below.
Ngā mihi nui
Great to get another interesting and entertaining blog from Colin Miskelly. If the flax weevils have moved to other islands in the area how would they have made the move if they are flightless?
Kia ora Olwen
Thank you for your feedback
How these flightless weevils could move between islands was discussed in a scientific paper published in 2018 (I suggest search “Tuhinga New locality records for two species of protected weevils”). This paper includes the comment:
“Possible ways that flax weevils could move between islands include hitching rides on or with people, and rafting on clumps of floating flax. Wharariki often grows overhanging the vertical shores on islands in southern Fiordland, and clumps are commonly seen floating in the southern fiords after storms”
Only one problem with this commentary – too brief! Great stuff; more, please.
Kia ora Denis
Thank you very much for your comments
More detail on the findings of the survey are likely to be published in the Birds New Zealand journal Notornis. Unfortunately researching, writing and publishing scientific papers takes a bit longer than blogs, but you could look out for Peta Carey’s book DUSKY – TAMATEA due out by October 2020 (Potton & Burton Publishing).
Seven scientific papers published in the journals Notornis and Tuhinga present findings of the 2016 & 2017 surveys. Most of these are freely available online, and can be found by web-searches using the following words:
Notornis Breeding petrels of Dusky Sound
Notornis Do grey-backed storm petrels breed in Fiordland?
Notornis Breeding petrels of Chalky and Preservation Inlets
Tuhinga Review of the distribution and size of gadfly petrel colonies
Notornis Dispersal of endemic passerines to islands in Dusky Sound
Notornis Dispersal of translocated endemic passerines to nearby islands in Chalky and Preservation Inlets
Tuhinga New locality records for two species of protected weevils
Ngā mihi nui