The battle against the great white butterfly pest appears to be working with detections dropping by more than fifty percent in autumn this year, compared to autumn last year.
The species is only found in the Nelson/Tasman region and DOC has been leading a programme to eradicate the pest out of concern for the threat it poses to our endangered native cresses. Successful eradication of the butterfly would be a world-first.
Catching butterflies is all in a day’s work for the team
The Nelson eradication team’s drive and determination will be a key factor in achieving that success. An example of that determination was on display recently when four of the team armed with nets chased a darting biggish white butterfly through at least five properties, across the road, and up and down hills, determined not to let it escape their clutches. Finally Ranger Maddie netted it. It proved to be an important catch: a female great white butterfly full of eggs that could have set up a new infestation in an area where butterfly finds had become few.
Female great white butterflies can lay up to 750 eggs
The team are not the only intrepid butterfly catchers. Team members searched gardens in one area for several days looking for a female butterfly suspected to be in the vicinity. It was duly presented to them dead by an elderly woman who in spite of poor eyesight had managed to trap the butterfly with a glass on the wall of her house.
This spring will be a pivotal time when the whole butterfly population emerges together from pupae, giving a good measure of its population status. DOC is working closely with the community to clear this major pest from the region and the country.
Rangers with nets at the ready in a large patch of wild brassicas that will be sprayed
Instrumental in removing cats from Te-Hauturu-o-Toi/Little Barrier Island, Dick Veitch returns, with 22 others from the 1970s eradication team, to delight in an island transformed. Here’s his story….
Arriving at Little Barrier Island
I was off the boat, through the quarantine shed and heading to grab the bunk of my choice when it hit me—the continuous bird song almost blasting across the flat. Incredible!
The others caught up, the kettle boiled, and we settled down for the official welcome from the island ranger. But he soon had to play second fiddle to a kokako happily drinking from the spouting. Incredible again!
The next day I almost tripped over a robin hopping from the quarantine shed across the track looking for food—just like the blackbirds and thrushes hopping over the lawn back at home. Incredible times three!
Kokako hopping about the grass like a common lawn bird
I returned to Te Hauturu-o-Toi, or Little Barrier Island in two shifts, with 22 of the 139 people who helped get rid of cats on the island in the late 1970s. Back then the forest was quiet. A visiting photographer at the time demanded “The forest is silent. Where are all the birds?” My response was “It’s mid-afternoon. What do you expect?”
The bird song is now continuous—mostly bellbirds, some kokako and saddleback, and the occasional tui. Birds sing day and night. I’ve been back to Little Barrier occasionally since it became cat free and seen the changes slowly building the magic of the place (not that we didn’t think it was magical before!). But what must be going through the heads of those who were with me who hadn’t been back to the island in more than 30 years!
The first group return. Standing left to right: Dave Garrick, Alice Murman, Tom Hardy, Richard Anderson, Terry Hatch, Geordie Murman, Rex Page, Leigh Joyce, Liam Walle, Phil Thompson, Mahina Walle, Richard Walle. Crouched left to right: Matt McDougal, Dick Veitch
The second group return. Left to right standing: Hans Rook, Andy Cox, Chris Smuts-Kennedy, Erica Law, Grant Fielder, Locky Charmichael, Richard Anderson, Viv Anderson, Mahina Walle, Gideon Anderson, Leigh Joyce. Crouched left to right: Tim Lovegrove, Louise McNamara, Dick Veitch, Liam Walle, Richard Walle.
The last cat was removed in 1980. We patted ourselves on the back and put saddlebacks back onto the island—cats had wiped them out in the 1880s. With cats gone we expected some seabirds to return, but knew the next pest down the line, the rats, would slow any bird recovery.
In 1980 no one had any idea it would be possible to eradicate rats from such a rugged 3,000 hectare island. But in the 1990s, when rat eradications from small islands were becoming standard, talk started up about getting rid of the rats from Little Barrier. And what do you know, the island was declared rat free in 2004!
Kiore/Pacific rat, Little Barrier Island, 1975
This was the real game changer. Cats eat rats and birds, true. But rats eat birds as well as insects, eggs, plants and seeds. With no cats and no rats, plants and birds are flourishing on Hauturu. This was expected, but the amazing thing is that some bird numbers have almost doubled, and plants we have only ever seen flowering are laden with fruit.
It will take time for lizard and seabird numbers to increase. Forest birds can have several nesting attempts each summer, but seabirds are generally limited to one egg a year, and lizards to two or three eggs or young, sometimes only every second year. But there have already been some amazing successes.
The most amazing find is the NZ storm petrel. Once thought extinct, sightings at sea off north-east NZ began in January 2003. Now a diligent team of seabird enthusiasts have found the bird breeding on Little Barrier. Just how this tiny bird survived the rats and cats remains a mystery.
Swapping stories at the bunkhouse. Left to right: Andy Cox, Richard Anderson, Gideon Anderson, Locky Charmichael, Grant Fielder
With the exception of the extinct Little Barrier snipe, all the birds decimated by the cats and rats are now back in abundance or still increasing. The banded rail, last seen in the 1940s, has been seen with chicks on the island, and a crake species, not previously seen, has also been sighted – just not well enough to see whether it’s a spotless crake or marsh crake.
There is surely more change to come but it is hard to imagine that it will be any more wonderful that it is now.
Thanks to DOC staff in Warkworth and on the island for their help in organizing our trip.
Dick Veitch is an expert in eradicating pests from islands. He worked for the Wildlife Service and DOC for about 40 years.
The work on Ulva Island continues to progress, with the work focussed on planning for an eradication option and obtaining the resource consent for this work.
Planning work is progressing well, key decisions have been made about bait storage, loading site, re-fuelling site etc and organisation of these and other aspects of the operation is well on track.
Documentation such as contracts (bait supply, aerial bait spread), operational plan etc are either completed or in final draft phase.
The operational plan has been sent to the Islands Eradication Advisory Group for feedback, (including questions raised by the community such as merits of pre-feeding and best practice for sowing the coast).
IEAG is a team of DOC experts who provide worldwide technical support for island eradication operations. New Zealand leads the world in this field and the meeting was attended by people from far flung places such as French Polynesia, California and the UK, all seeking advice on how to go about eradicating rats from islands.
Calibration of the helicopter buckets has been organised for the last week of April (April 27th). Bucket Calibration is an important step in the eradication process and is carried out in a flat mowed paddock where all bait can be seen and counted. Non-toxic bait is sown through the bucket that is to be used in the operation and the machinery is tweaked to ensure that bait is sown to the correct swath width (i.e. width of strip sown with bait on each pass) and that the correct number of pellets per hectare are sown. Once the correct bait application spread and rate has been achieved the bucket settings are noted so that the toxic bait can be spread correctly on the day.
As mentioned in the last update, a public meeting will be held at 7.30pm on 28th of April in the Stewart Island Community Centre. This meeting will discuss any and all ideas about possible ways to improve the biosecurity on Ulva Island to further reduce the chances of rats establishing in the future. If you have any ideas, or are simply interested to hear what might be proposed, please come along.
The University of Otago’s bird research group (who monitor robins on Ulva Island every summer) have offered to monitor the effects of the baiting operation and the effects that the rats have had on the birds on Ulva Island. It will be great to have this independent monitoring of the operation.
Some confusion seems to have arisen around the reasons as to why we have stopped trapping on Ulva Island.
The long term exisiting biosecurity measures on the island are aimed at preventing a rat population becoming established. In this case, they have failed and a rat population has established. Continuing to run these traps and bait stations will not even now slow the rat population expansion and is therefore considered to be a waste of time. Servicing them has stopped so we can focus efforts on a proper eradication attempt. This has been misinterpreted by some as DOC giving up. The fact is that we are well down the planning track for an aerial eradication attempt.