Ducks Unlimited
Monday, 22 July 2019 02:47

Trapline volunteers

Eleven volunteers from the New Plymouth branch of PricewaterhouseCoopers spent a day out of the office as they helped replace over 90 stoat traps along the Curtis Falls Track in the Egmont National Park.

The old traps came out of the boxes and new stainless steel ones went in. Replacing a line like this can take a couple of weeks so the volunteers really made a difference. With each person carrying six traps in and another six out as well as some tough climbs along the way, it was a big day.

This trap line protects the whio living along streams and rivers such as the Maketawa and they form a network that covers around 7000 hectares. Last year was a record year for whio ducklings in the Park with 33 ducklings hatching in the wild.
Another volunteer, Ian Street enjoys the Onaero Domain where he spends a lot of time at his Onaero beach batch and helps out by looking after a trapline and keeping an eye on weeds in the local reserve.
A whitefaced heron also enjoys the Onaero Domain and batch dwellers say he’s been around for about 14 years. “He had a mate,”said Ian, “but she died some time ago.

Recently though he’s found another.” 
The heron seems to know when Ian’s at home. He walks up to the front door and taps on the door. “He visits regularly,” said Ian. “I give him a little bit of fresh mince sometimes and away he goes.”

Whitefaced herons are New Zealand’s most common heron. They arrived from Australia in the 1940s so they’re considered native. This one’s been around long enough to be called a local.


Published in Issue 159
Monday, 22 July 2019 00:26

Pateke success at Tawharanui

Pateke success at Tawharanui

Tāwharanui Open Sanctuary reintroduced pateke between 2008 and 2010, with 148 captive reared ducklings released in total. An earlier release in the 90s failed due to inadequate predator control, an unfortunately common occurrence for pre 2000 pateke releases.
More recent releases within the predator free open sanctuary have successfully established a population of approximately 30 pair, with pateke and ducklings regularly seen throughout the park. Tāwharanui pateke have also dispersed from the park and have established as two new satellite populations at nearby Christian Bay and Omaha, as well as supplementing remnant population on Kawau Island.

Matt Maitland
Senior Ranger Open Sanctuaries
Northern Regional Parks


Published in Issue 161
Monday, 22 July 2019 00:13

To save Pateke

To save Pateke Knowledge, care and endurance

Positive aspects of the recovery programme

The release of captive reared Pateke by Ducks Unlimited (NZ) in the Northland area between 1980-1992 had a number of positive outcomes, particularly at the 350-hectare government owned Mimiwhangata Farm Park during a brief period when predator control was being carried out. 
Pre-release aviaries were used and supplementary feeding took place.
3½ half months after the release of 64 captive reared Pateke at the Mimiwhangata, Farm Park in 1986 all 64 Pateke were believed to be still alive (Hayes 2002).

1. Flock mating/natural pairing of Pateke was the key to the highly successful captive breeding programme – together with the enthusiasm of participants. Flock mating is now being used in a number of rare waterfowl recovery programmes.

2. Captive reared brown teal adapt readily to a wild environment, natural or created.

3. In Northland captive reared Pateke released at Mimiwhangata, Whananaki and Purerua between 1986-1992 survived for long periods and produced offspring – in spite of little predator control, with predator control Pateke are doing well.

4. Where predator control programmes have been in operation at suitably selected quality release sites in Northland (and more recently on the Coromandel) Pateke have survived very well and have successfully reared many progeny.

5. In the absence of waterfowl hunting and predators, captive reared brown teal released into quality Pateke habitat have few problems adapting to the wild.

6. A gradual transition from captive bred to wild, using pre-release pens and a supplementary diet was successful.

7. Brown teal are by far the most predator vulnerable species amongst all species of waterfowl

8. Captive reared teal released on off-shore islands that have suitable predator-free habitat survive and breed well.

9. When the release of captive reared Pateke into quality habitat is coupledwith predator control, a pre-release aviary, supplementary feeding and with the site having an adequate area for a significant population increase (such as at: Mimiwhangata, Purerua and Port Charles), the recovery process is a very simple one!

10. Between 1969-1992 it was learnt that releasing captive reared Pateke at a large number of unsuitable and disconnected habitats, with 35 different sites being used, achieved little, was counterproductive and very expensive.

11. Since the 2000 Audit of the recovery programme steady progress has been made towards increasing the wild populations of Pateke.

Starting in 2009 a150 captive reared Pateke have been released in Fiordland, but it is too early to predict the outcome of this programme. 
Pateke were once widespread throughout Fiordland, the habitat is still excellent and with ongoing predator control a South Island population could be re-established.

The 2000 audit of the pateke recovery programme

As already discussed, in late 1999 the Department of Conservation carried out a major audit of the Pateke Recovery Programme, into which 39 people with Pateke experience had input. The outcomes were published in 2000.
Since the Audit set down clearly defined recommendations and objectives of what needed to be done to save Pateke from extinction there has been a remarkable turnaround - from a total population of 800 in 1999 to a population of 2000 by 2012, with 350 in Northland, 550 on Great Barrier Island, 650 on Coromandel Peninsula, 200 on off-shore island.

Recovery mode

The population chart shows there has been significant improvement in Pateke numbers since the 2000 Audit; this has been achieved in three historic Pateke areas of the North Island mainland; at the Mimiwhangata Farm Park, Whananaki, Tutukaka, Ngunguru, and Purerua Peninsula all in the Northland region of New Zealand, on the Coromandel Peninsula and on Great Barrier Island - all areas where Pateke were extant in 1999. The key to the recovery has been the introduction of major predator
control programmes using a variety of trapping techniques, in association with Pateke habitat creation, habitat enhancement, protection and management, no duck hunting, and in Northland and Coromandel Peninsula the release of significant numbers of captive reared Pateke.
By 2012 the Pateke population in Northland had risen from 350 in 2000 to 550. The most spectacular re-establishment has taken place on the Coromandel Peninsula, where from 20 Pateke in 2000 the population had risen to 650 by 2012.

The recovery on the Coromandel clearly endorses the philosophy that provided Pateke have suitable habitat, protection from predators and ongoing management support they will survive and breed very  successfully, with the success on the Coromandel possibly being the most rapid recovery of an endangered duck.
Since the 2000 Audit there has been major predator control.

Negative aspects of Recovery programme

Between 1975 and 2002 there were 2000 Pateke released into mainland wetland sites, with all releases failing to slow the species decline, largely due to:

• Lack of continuity amongst Pateke management personnel and others directly involved in planning the survival of Pateke. 

• Sites used were poorly selected.

• No pre-release study to see if there was an adequate food source.

• No pre-release study to determine whether the habitat was suitable.

• Little predator control and little knowledge of the subject.

• Little understanding about the main predators to control/ eliminate.

• Until early 2000 no sites had ongoing predator control.

• Many sites were out on a limb, with no wild Pateke in the area. • Many sites had no adjacent wetlands for progeny expansion or to which adults could escape.

• Many sites had no loafing facilities or aerial protection.

• Insufficient supplementary feeding of released birds. The value of this is recorded in a paper published in 2013.

• Pre-release aviaries rarely used.

• Competing waterfowl were present.

• Hybridisation with mallards and grey teal occurred. 

• Instant dispersal of released birds occurred.

• A lack of ongoing support.

• A lack of monitoring of released birds.

Published in Issue 161
In early August Steve Playle completed the trapping maintenance down at the wetlands for the month. It was the first servicing of equipment for the new financial year.
Result were 7 ferrets, 2 weasels, 6 rats, 3 hedgehogs, 3 harrier hawks and 2 magpies.
“We have cracked 50 ferrets since trapping commenced last July. A big tabby cat was swimming from the new Wairio bund out to the sprayed willows when I approached it on the quad. Pity I wasn’t carrying a firearm as it would have been easy to dispatch. Water levels were very high in places so some traps were
not able to be serviced.
“I saw a slate grey Bittern in the Mathews drain almost opposite where DoC launch their boats in Boggy Pond. I saw a second darker coloured Bittern at the southern end of the Stage one area of the Ducks Unlimited Restoration block. Great to see!”
Heavy rain prevented Steve from getting traps out at that time but he was out again the next week. Lake Rototawai was serviced also. He also took a cat, 1 rat, 1 hedgehog and a mouse from traps at Te Hopai Lagoon.

Steve regularly services traps in the areas we monitor. In July, almost 12 months since the first Timms traps went on the ground at Boggy Pond/Wairio Wetlands he caught 3 cats, 4 ferrets, 2 weasels, 4 rats, 12 hedgehogs, 4 mice, 6 magpies and 1 harrier hawk.

For the year total predators removed from this job are; 20 cats, 43 ferrets, 1 stoat, 13 weasels, 159 hedgehogs, 52 rats, 29 mice, 10 magpies, 2 harrier hawks and 1 rabbit.
During duck shooting season Steve reported we lost a total of 3 DOC 250 traps and 2 Timms traps to light fingered people.
Steve also did the first service of the Lake Rototawai predator control sites on July 4 and cleared 2 cats, 2 hedgehogs and 1 mouse from the traps. All bait stations were empty of bait too. The Te Hopai Lagoon traps were serviced and he took 2 very large cats, 3 hedgehogs and 1 mouse from those traps.
Wario September 5  - Steve completed trap servicing down at the wetlands for the month. Predators caught were 2 cats, 6 ferrets (plus one that Jim Law took from a trap making a total of 7), 1 weasel, 3 rats, 8 hedgehogs, 8 mice and 2 magpies.
Steve reports he saw a Bittern about 60 meters south of the viewing hide on the Boggy side of the stop bank and he saw another at Pounui Lagoon.

Steve will have commence fortnightly servicing of the traps at both of these
operations until breeding season is finished around the end of February.

“As a matter of interest we have already caught 14 ferrets at the Boggy/Wairio wetlands for August and September so it just shows we cannot take the handbrake off regular predator control any time soon,” said Steve.


Published in Issue 161
Thursday, 04 April 2019 10:43

Trapping at Boggy/Wairio

Trapping at Boggy/Wairio in April by Steve Playle resulted in the following critters recorded - 4 cats, 1 ferret, 9 rats, 3 mice, 1 magpie and 17 hedgehogs. 

The grand total came to 15 cats, 36 ferrets, 1 stoat, 9 weasels, 130 hedgehogs, 46 rats, 21 mice, 3 magpies, 1 harrier hawk and 1 rabbit.

Steve also saw a Bittern in Boggy Pond down where the culvert pipes are beside the Boggy stop bank. That photo is on the front cover.

Steve has since put in other trap sites along the new track to the viewing hide out by the spillway.

Published in Issue 160
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