Ducks Unlimited
Monday, 26 November 2018 08:15

Predator Free New Zealand

Maybe - but not just yet

 

Counting every rat, mouse or mustelid trapped may be satisfying, but it is irrelevant in the war against predators and may be lulling us into a false sense of security, guest speaker Professor Carolyn (Kim) King told DU members at the conference.
 
In her speech, Maximising the Duck Harvest, Prof King, from the School of Science at Waikato University, thanked Ducks Unlimited, which like many hunting clubs around the world, had turned itself into a conservation group, supportive of conservation research organisations and with members who were observant naturalists contributing to conservation efforts.
 
She said a good harvest operation:
  • aims for a sustainable yield
  • never takes more individuals than the population can replace
  • can be like the constant harvest by rabbit trappers, deer cullers, and predators
  • a population can’t be affected if the yield is not declining.
 
As an example, she said, the winning team in the Great Otago Bunny Hunt in 2012 bagged 1035 rabbits as its contribution to the 10,424 tally from the 24-hour event. During the 21 years of the event, 253,735 rabbits have been killed (mean: 12,082 a year) but it has made no difference to rabbit numbers.
 
Harvesting is a dynamic target-habitatpeople system in which:
  • protection of a valued resource can be ineffective unless broader ecological/ sociological context is understood
  • the interaction of resource/habitat/ people defines the outcome
  • solutions require strategic organisation, stakeholders agreement and effective methods
  • the biology and strategic organisation determine effective policy (which DU does very well).
 
Using an example from Wiltshire in the UK she demonstrated how a predator control experiment produced a surprising result. In two areas of farmland, 1km apart and with similar habitat, predators were controlled in one area for three years and then in the other area for three years.
 
The study had been based on the assumption that habitat on UK game estates was the only important factor but the results clearly showed a big increased harvestable yield of grey partridges in whichever area was subject to predator control.
 A computer model developed from the study predicted that the highest populations would be found where nesting cover for the partridges was increased and predators were removed, even if shooting was permitted as well. Key is the interaction of habitat (controls productivity) and shooting mortality. If nests are protected, more young survive, so shooting can substitute for nest mortality caused by predators.
 
Using a NZ example to highlight the relationship between habitat and mortality, Prof King referred to wetlands in the Upper Waitaki area. In 1850, wetlands and swamps covered 71,000 hectares, but the effects of human activities has been devastating with 7300 ha swamps converted to pasture, more fragmented; 22,300 inundated by hydro electric schemes; 4200 ha braided riverbed dewatered (9% loss); 22,300 ha new open water habitat + 300 km more shoreline which doesn’t suit riverbed birds; predation is heavy and breeding rate low on the remaining 41, 700 ha wetlands (40% loss).
 
Food supply has the greatest effect on bird populations. The braided riverbeds were dewatered or turned into open water habitat, which did not suit the birds adapted to feeding on the riverbed, exposing them to predation and a drop-off in breeding.
 
Prof King said the deadliest predators for ducks were egg-loving hedgehogs, ferrets, stoats, rats, mice and cats. An Upper Waitaki Basin study of predation on the nests of dotterels, terns and stilts showed that cats, ferrets and hedgehogs did the most harm to nesting birds in that area.
 
She said, “We know we can kill predators, so what’s the problem?” Counting a pile of dead pests can be enormously satisfying but it does not tell us what we want to know, which is how many are still there, how to account for those that replace those dead ones, and how to know if we have taken out enough predators to benefit the birds we want to protect. That boils down to what actually determines the numbers of animals – both the predators and the birds.
 
Ferret numbers are controlled by rabbits (their main food source), not trappers. The rabbit yield is not declining: rabbits and ferrets are co-evolved prey.
 
A pilot trial in 2005 presented another serious problem – trap avoidance. Radio-collared ferrets in a study near Tokoroa were tracked by an aircraft which flew over the area during the day.
Nine of the 15 ferrets were located. Monitoring sites showed that six of the ferrets made 22 approaches to 2 experimental recording sites, which could have been traps, but only three entered the tunnels. On the final extensive trap-out, four of the 15 eluded capture, although their radio signals confirmed they were still there.
 
The following year collars were put on 30 ferrets west of Lake Taupo and a new toxic bait dispenser was used. Over five weeks, only 12 visited the bait stations and only eight took the bait. The monitoring regulations said every ferret had to be accounted for but of the 13 known survivors, only two could be caught.
 
In kiwi sanctuaries in Northland, stoats were refusing to go into the bait tunnels and it was only a brief 1080 operation that stopped the decline of kiwi chicks. Though it is awful stuff, we have to use the tools we have until we come up with something better, she said.
 
Predators are intelligent and quickly learn to avoid new devices presenting danger to them. In Britain, American mink, which escaped from fur farms in the 1950s, had become a serious threat to the native water vole (Ratty in Wind in the Willows). The mink, like rats, are good swimmers which means they can avoid land traps set on river banks. The problem was tackled by using traps placed on floating rafts, which might be appropriate to adapt as a control for Norway rats here, Prof King said.
 
 
New technologies are absolutely essential and can transform results. She said at a 1976 conference that she attended senior scientists said rat eradications on islands were impossible, but they were wrong. The invention of brodifacoum in the 1980s plus precise bait placement enabled Breaksea Island to be cleared of Norway rats in three weeks in 1988.
 
“That’s what we need – some kind of new technology that will break the mould, something different... One of the definitions of insanity is to keep on doing the same thing and expecting different outcomes,” Prof King said.
 
We can and must increase the intensity of predator control, but to be effective it must add to the natural mortality. Mustelids were introduced to control rabbits but rabbits were breeding at a faster rate and their numbers were unaffected. The mustelids were only substituting for natural mortality.
Only when rabbit breeding is reduced for other reasons (drought, 1080), can mustelids and/or trappers add to their normal losses, and achieve a real effect
Failures were usually due to some combination of:
 
Human attitudes
  • Forgetting that nature is on the predators’ side and ignoring the effects of natural selection
  • Counting numbers removed, not numbers remaining,
  • Lack of coordinated, agreed strategy
  • Lack of flexibility in response to experience
  • Insufficient stakeholder support.
 
Inadequate technology
  • Inefficient tools
  • Failing to deploy combination of methods
  • Having no effect on fertility, immigration.
 
Prof King said, on the other hand, some of the common features of successful predator control were a combination of:
 
Human attitudes
  • Operator confidence, meticulous preparation, sufficient funding
  • Never repeating mistakes, never giving up, so accumulating improvements, combining/switching strategies when necessary
  • Landscape scale coordination
  • Strong community support.

​New technology

  • Adds to natural mortality
  • Prevents immigration
  • Targets fertility
  • Confirms benefit to native species.
 
Prof King concluded by saying Predator Free NZ was still a long way away but “don’t despair, history is encouraging!”, and DUNZ would play an important role.
In the meantime we must keep using whatever tools we have so we still have native species surviving by the time we develop something better, protecting duck nesting sites is possible and needed now.
 
PFNZ is going to be much more difficult as it requires development of as-yet-unknown, 100 per cent acceptable methods to control predator replacement rates.
 

 

Published in Issue 175
Monday, 26 November 2018 08:06

Waipa wars – from muskets to mustelids

Peat lakes and battle sites were the main themes of this year’s bus trip at conference courtesy of Ducks Unlimited’s knowledgeable tour guide Tony Roxburgh.
 
Tony is the Waipa District Council’s heritage and museum manager and he also wears another hat – as Wetland Trust of New Zealand Chair and Trustee. He took DU members on a nature, culture and history tour of the Waipa region.
 
The first point of interest was Lake Rotomanuka, one of about 16 lakes in the Waipa District. It was once one lake but is now two separate bodies of water. Around the lakes, public walkways, buffer margins and sediment traps are being developed by Living Waters, a partnership between the Department of Conservation and Fonterra.
 
Native eels and smelt can still be found in the lake but have been joined by introduced species: rudd, carp, koi carp and catfish. First stop on the bus trip was the Lake Serpentine/Rotopiko sanctuary. It is enclosed by a predator-free fence, which was built with a $500,000 grant.
 
The 50-hectare sanctuary is thought to be mammal free after mouse incursions were curtailed by extending the fence netting down into a trench dug along the fenceline.
But the project hasn’t been all smooth sailing. As well as having to put its planned $5 million-plus visitor centre on hold, the sanctuary had encountered an unforeseen problem – once news of the avian safe haven got out to the passerine community, thousands and thousands of starlings, sparrows and finches were swooping into the sanctuary at dusk to sleep overnight.
 
They leave behind mountains of guano, which, over time, would change the chemistry of the peat lake.
 
Tony said deterrent measures such bangers and laser lights were being trialled.
 
Releases of kiwi and takahe are on the sanctuary’s wish list but pateke (brown teal) will be the first species to be introduced. Tony said the visitor centre project would be replaced with a more modest and modular alternative – beginning with a three-bedroom house for volunteers and school groups to stay in. With no electricity on the site, the house will have solar panels, and a composting toilet.
 
Following a hearty buffet lunch at the Five Stags restaurant in Pirongia, everyone boarded the bus for the nearby Alexandra Redoubt. This fortification was constructed by the constabulary after the land wars in case Maori tried to take back their confiscated land.
 
During the tour, Tony pointed out many other historical landmarks, including pa and battle sites, and natural features such as the volcanoes and kahikatea stands dotting the landscape.
 

 

Published in Issue 175
Monday, 26 November 2018 07:25

CONFERENCE REPORTS

Neil Candy reported that Jim Law had replaced Ken Cook as a trustee on the Waterfowl and Wetland Trust, which was “ticking along really well” with more than $500,000 in the bank.

Wetland Care

Reporting on the work of Wetland Care, Will Abel said $10,800 had been spent on three wetlands in the past year, creating about 10 acres of wetland

ROYAL SWAN
Neil said the successful breeding of royal swans had been declining but fortunately had coincided with a drop in inquiries for them. The reason for the lack of breeding success was unknown and the few lightweight birds available from Peacock Springs in Canterbury meant it was difficult to tell the boys from the girls to find a breeding pair. Compatibility was another problem, with one bird sometimes killing its intended mate.
 
WHIO
Neil Candy reported, on behalf of Peter Russell, that whio had had their best breeding-for-release season. Seven pairs in the North Island produced 75 eggs, with 46 surviving to be released. Of those birds, 15 went to Egmont National Park, 23 to Whanganui National Park and 8 to Tongariro National Park. In the South Island, four pairs produced 45 eggs, with 30 released, all in rivers around Hokitika.
 
PATEKE
Meanwhile, pateke in Northland have benefited from predator control introduced to protect kiwi in the area, and the ducks are now established from Mimiwhangata to Pataua North

BITTERN

Emma Williams reported that of one of four bitterns fitted with a transmitter at Lake Whatuma was missing, but it was hoped it would return for the breeding season. DU still has two transmitters to place.
 
Four other transmitters had been placed on chicks found starving in urban areas. They were rehabilitated and two were released in BOP and two in Canterbury. One has survived two years on and its transmitter had just died.
 
WEBSITE
Paul Mason explained the layout of the new website which is now on a new platform and is more accessible to devices such as tablets and smartphones. Visitor numbers and search results for the website were healthy.
 
NZ GAME BIRD HABITAT TRUST
John Cheyne reported that the trust has allocated $96,000 in 2018 for 24 projects throughout New Zealand. In 2018, the trust had received 21 applications for funding to assist with wetland restoration and creation
 
 

WAIRIO WETLAND

Jim Law reported that restoration work at the Wairio wetland this year had cost $9500, bringing DU’s total expenditure over the 13 years since the project began to more than $215,000.
 
A plan to divert water from Matthews Lagoon to the wetland on its way into Lake Wairarapa was still awaiting approval from the Greater Wellington Regional Council. 
The council was continuing its predator control and its traps were serviced three or four times a year. Large numbers of mustelids and feral cats are still being caught, highlighting reinvasion as a serious problem. DOC was doing a good job of maintaining the bund wall walkways.
 
Wairarapa Moana, which encompasses Wairio, is included in a Treaty of Waitangi settlement, meaning ownership of the wetlands will be transferred to Ngati Kahungunu and Rangitane. Ngati Kahungunu, the principal iwi owner with 90 per cent, has indicated that it would like DU to carry on with its work and it will be business as usual. The iwi also wants to re-establish a Lake Wairarapa committee and it would like DU to be a part of that.
 
 
Published in Issue 175
Monday, 26 November 2018 07:17

Decisive year ahead for Board

 

Where to from here will be the big question facing the DUNZ Board in the coming year. President Ross Cottle, in opening the formal business of the 44th AGM, said that, with an ageing membership and fewer members keen to do the work, the future direction of Ducks Unlimited would be on the Board’s agenda this year.

Measures already in place or under consideration were making Flight a two-yearly publication and changing the conference to a biennial event rather than yearly. With fewer demands to create new wetlands and maintain the established ones, the Board would be looking at other ways, including research scholarships, to support DUNZ’s goals.

Ross thanked John Cheyne, who resigned earlier in the year, for his four years as president and for raising the profile of bittern. Ross also paid tribute to those members who had passed away during the past year: Ian Pirani, Nancy Pain, Audrey Pritt, Alan Wilk and Robin Borthwick. Joyce Brooks also passed away after the AGM.

Treasurer John Bishop presented the accounts and updated members on the new rules for charitable trusts, which require entities to state their purpose. DUNZ had submitted the following mission statement: “We deliver and advocate for effective wetland restoration, development, research and education; and support the preservation of threatened waterfowl and the ethical and sustainable use of wetlands.”

Published in Issue 175