Viewing entries tagged
2020

Great news: Native birds are beginning to recover in the Perth River valley!

December 16, 2020

We are delighted to report that native birds have begun to recover in the Perth River valley, just 18 months after our winter 2019 predator removal operation successfully eliminated stoats. In July, follow up actions removed the last resident possum, and we have now almost finished off the last few rats.

We recently analysed almost two years’ worth of native bird detections from our network of 142 lured trail cameras. In the graphs below, these detections are broken down by the percentage of the camera network that detected each species every seven days.

Note:

There are currently two gaps in the data, on November 1-21 and April 14-28, in which footage has not yet been processed. We will update the graphs as soon as this footage review is complete.
The camera network has also infrequently detected ruru (morepork) throughout the survey period.

The lured camera network is low to the ground, and is designed to detect possums, rats and stoats, not native birds. Therefore, these incidental records are unlikely to show the full extent of recovery as a result of the predator elimination. Nevertheless, this network has provided us with rich data about the activity and relative abundance of a wide range of species within the Perth River valley—demonstrating once again the versatility and value of this camera tool.

Highlights

Kea

*Juvenile kea in the Perth River valley, March 2020 (Chad Cottle)*

The Kea Conservation Trust (KCT) and DOC have reported that kea up and down the West Coast double-clutched (mated and raised fledglings twice) during the 2019-20 breeding season.

Our observations in the Perth River valley support this conclusion. Fledgling kea were spotted in the site as early as October 2019, and as late as March 2020, and young kea in different age classes have been seen within the same period. This indicates that kea have had a very successful breeding season, which is likely to be significantly enhanced by the absence of stoats in the valley.

Both ZIP team members and experienced helicopter pilots continue to report frequent kea sightings during their work in the field site, including a memorable encounter with 13 juvenile kea in February 2020, and another with 27 juvenile kea in April 2020.

Kākā

Before the predator removal operation, no kākā were detected on camera in the Perth River valley. Kākā were first encountered by our field rangers in the field site in August 2019, after the completion of the operation. Adults and juveniles have since been detected in the camera network on several occasions, by 12 different cameras throughout the site.

In June 2020, two of our field rangers captured the footage below of a kākā feeding on a rotten standing tree trunk near the confluence of the Perth and Barlow Rivers. Since September of this year, our team has reported increasing sightings of kākā within the same area. In November 2020, kākā were seen for the first time in both the Teichelmann Creek and Lower Barlow areas.

Kākā nest in holes in tree trunks. This makes them extremely vulnerable to predation by stoats, which can kill eggs, chicks and incubating adults in a single attack. A five-year study at Lake Paringa, South Westland, between 2010 and 2015, found that thirty times more kākā chicks were produced in an area after 1080 treatment than in an area where no 1080 was used.

We are therefore pleased, but not hugely surprised, that the successful elimination of stoats from the Perth River valley has led to an increase in kākā sightings. We look forward to seeing this population thrive!

Yellow-Crowned Kākāriki

Before the predator removal operation, yellow-crowned kākāriki were very infrequently heard by our field rangers during the course of their work. They are now regularly heard by field rangers up and down the Barlow Valley, and have been seen beneath the forest canopy on several occasions, including the sighting below in October this year.

Kererū

*A kereru caught on camera in the Perth River valley, June 2020*

Before the predator removal operation, kererū were frequently sighted by our field team. However, no kererū were detected in our camera network until after the first phase of the operation. Over the last year, our team members have regularly seen kererū throughout the field site, and have even occasionally encountered large flocks of 30 or more birds!

Whio

Whio (blue ducks) were detected on just two cameras in the field site during 2019, before the predator removal operation, and on four cameras in 2020. The relatively low number of detections is not surprising, given that whio live on the river, and the camera network is primarily located in the bush! During the 2019-20 breeding season, whio ducklings were spotted on several occasions by members of the ZIP field team in the upper Barlow River area—the first time since we began work in the site in early 2018. In November 2020, rangers reported seeing whio ducklings in two tributaries of the Perth River.

Female whio are especially vulnerable to stoats during the nesting season, and rats and possums have been known to destroy whio nests and eggs, so the elimination of these species is expected to have a positive impact on the Perth River valley whio population.

Whio naturally live at low densities on the large, flood-prone rivers of South Westland, with an average of 1 pair per km of river. The modest increase in whio sightings and detections we have observed since the predator elimination is a very positive indication that the population is beginning to recover in the absence of predators.

Tauhou (silvereye)

Interestingly, silvereye activity appears to be highly seasonal, with dramatic increases in detections during the winter months, and reduced activity during the warmer months. So far, there has been no observable impact either way on the population as a result of the predator elimination.

Ngirungiru (tomtit)

Ngirungiru activity also appears to be highly seasonal; however a general increase in detections can be observed following the predator removal operation. In February 2020, seven months after the operation, ngirungiru detections peaked at 22%, compared with 15% in February 2019.

Ngirungiru are frequently seen by our field team in all areas of the field site.

Kakaruai (South Island robin)

Our team regularly see kakaruai around the Perth River valley. The bird pictured above is a regular visitor to ZIP’s bivvy in the Upper Barlow area.

The footage below was recently captured by one of our field rangers near a tributary of the Barlow River, where a friendly kakaruai cleaned her boot and gaiter.

Kārearea (falcon)

Kārearea are frequently seen and heard around the Perth River field site, including one that is regularly sighted near the Upper Barlow bivvy.

Ruru (morepork)

Ruru photographed in the Perth River field site, July 2020 (Chad Cottle)

Ruru are occasionally seen and heard by our field rangers, and detected by our camera network.

The ruru above was photographed by one of our rangers in July 2020 near a tributary of Scone Creek, after it landed nearby looking rather unhappy to have been woken up!

Koekoeā (long-tailed cuckoo)

Koekoeā have been regularly heard throughout the Perth River valley during spring and summer 2020, particularly around the Upper Barlow River area.

Tūī and korimako (bellbird)

Camera detections of both tūī and korimako have increased during the last year, and both species are regularly seen and heard throughout the field site.

RTL700A0_2020-09-15T13-11-44_Tui - Prosphenadera novaeseelandiae_1_2.JPG

Update on Perth River valley work programme – possum freedom achieved

July 1, 2020

Our intensive possum detection and response effort in the Perth River valley field site over the last 12 months indicates that we have now achieved possum freedom in the site. This is a major milestone, which has not (to our knowledge) ever been achieved at this scale on the New Zealand mainland.

Possum freedom means that we have removed all of the possums we knew to be present, and therefore we are confident that if any possums do remain they will be so few that they are unable to re-establish a viable population.

Since the aerial spot treatment, aimed at rats, in March 2020, we have been carrying out ground-based detection with our network of 143 lured trail cameras, and then targeting our response actions to those locations where possums are detected. We have now been searching for over 14,000 detection nights, and have removed the three possums detected during that time.

How we got there

Predator removal operation (Phase 1)

13 April 2019

After Phase 1 of the predator removal operation, an estimated 8-10 possums were detected in the field site. We live-caught one of these, fitted it with a VHF collar and monitored it through to Phase 2 – when it was removed.

Predator removal operation (Phase 2)

23 July 2019

In the 11 months following Phase 2, an estimated 5-6 possums were detected in the field site.

Decision to delay targeted ground-based removal of survivors

We began to detect a small number of possums in the field site 36 days after Phase 2 of the predator removal operation. However, we did not begin work to remove these possums until December 2019, primarily because the 1080 caution period following Phase 2 meant that Pepper, the possum dog, was unable to enter the site for several months. Possums are relatively slow breeders, so we considered that we had time on our side in which to effectively target possums before the population became unrecoverable.

During this time, we also began to reassess our approach to detecting and responding to surviving or invading possums. We had originally planned to deploy a permanent lean network of ZIP PosStop possum traps that included a ‘SafeLock’ mechanism to enable the traps to be locked during daylight hours, when kea are most active. A trial between December 2018 and July 2019 found that, while the SafeLock mechanism was successful in preventing unwanted trigger events, over time kea learned to interfere with the trap and compromise its capture effectiveness.

Then, in December 2019, we discovered evidence that a small number of rats had survived the predator removal operation and begun to breed within the field site. Removing these rats before the emerging population could spread became our most urgent priority in the site.

Spot treatment to target rat breeding

5 March 2020

We carried out a targeted aerial ‘spot treatment’ operation to remove the emerging population of rats before it could spread. Although rats were the target, we believe that this spot treatment was responsible for eliminating 2-3 of the surviving possums, with no possums detected in the Lower Barlow area, or in the Perth/Barlow confluence, after the operation.

On 19 May, a ranger discovered a partially decomposed possum carcass near the Perth River. This left us with an estimated 2-4 possums to remove.

Three possums successfully removed by detection and targeted response

19 May, 11 June and 29 June 2020

The detection and targeted response strategy has successfully removed the remaining three possums detected in the block.

The first of these is thought to have been the sole invader to date, as it was not detected in the field site until 8 March, roughly eight months after the predator removal operation. The detection location – near the head of the Barlow River – is an area we consider to be at increased risk of invasion, due to the lower flow of the river in this area. This individual was a 3kg female possum, caught on 19 May in a cage trap after being tracked by Pepper and Mike. Camera detections were used to narrow the initial search area.

*The 2kg male possum caught in the Teichelmann area on 11 June*

*Pepper the possum dog - one half of our impressive possum-hunting team in the Perth River valley*

The second is assumed to have been a survivor of the predator removal operation, which was first detected in the Teichelmann/Upper Perth area on 24 August 2019. This possum was a 2kg sub-adult male, caught on 11 June in an automated cage trap after being seen in that location on the camera network.

The third possum is also believed to have been a survivor of the predator removal operation, and was first detected in the Teichelmann/Upper Perth area on 11 September 2019. Again, trail cameras enabled us to hone in on a targeted area, where we livened automated reporting cage traps and set Pepper and Mike to work. The possum was caught on camera several times next to, and even on top of, the automated cage traps, only increasing the determination of the response team to catch it. On 29 June, our persistence paid off, and the possum was finally caught in an automated cage trap. The possum was a 3.3kg female, with no evidence of pregnancy, which is great news.

While we were already confident that possums were functionally extinct in the field site, catching up with this last known individual really builds confidence in our ground-based toolset and approach. We know that the job is not over, and we need to keep protecting the Perth River valley site from the ever-present risk of possum invasion. We will continue to systematically survey the field site for possums, using Pepper and the camera network, to keep building our confidence in the rivers as effective barriers to possum reinvasion. And, just in case, our response tools remain at the ready!

Our work in the Perth River valley is made possible by the support of the Department of Conservation, NEXT Foundation, and Predator Free 2050 Limited.

ZIP and COVID-19, May 2020 – a letter from our Chief Executive

May 25, 2020

Kia ora,

I hope this finds you and your loved ones safe and well after what has been a strange and, at times, challenging few weeks.

With the recent easing of restrictions under COVID-19 Alert Level 2, I wanted to take this opportunity to provide another update on the status of the Zero Invasive Predators (ZIP) team and our programme of work.

During the Alert Level 4 lockdown period, all field work at the Perth River valley site was on hold, and only animal husbandry tasks (i.e. no trials) were carried out at Lincoln. All staff who were able to work from home did so, including our field team, who shared a house in Hokitika and were ironically a lot less socially isolated during this time than they are used to being!

On 28 April, the beginning of the Alert Level 3 period, the field team returned to work in the Perth River valley (a site re-entry that was particularly memorable for one of our rangers), and we resumed trials and the supply of products at our predator behaviour facility in Lincoln. We developed new safety procedures for both sites, to protect our people and manage any public health risk associated with returning to work. Where possible, the rest of our team continued to work from home during the Level 3 period, and many team members are continuing to do so through Level 2. We remain in regular contact by phone, email, video conferencing and the magic of social media.

Our network of lured trail cameras in the Perth River field site has revealed that a small number of rats survived the spot treatment operation that we carried out earlier this year, and are very likely to have begun to breed during our absence from the site. Given the speed with which rats can re-populate, removing these rats before their population can spread has become our most urgent priority in the Perth River valley. We are using a range of targeted ground-based methods, including traps and bait stations, to achieve this.

We have also begun work to remove the 3-5 possums that survived the predator removal operation, and to remove a small number of invading stoats. Both responses involve deploying ground-based methods around the locations where these animals have been detected on camera. We are pleased to report that, on Monday 18 May, our ranger Mike and his dog Pepper successfully removed one of the possums from the site!

We will continue to notify you as soon as possible about any significant developments that affect our programme of work. In the meantime, please don’t hesitate to contact us if required.

Wishing you all the very best, and thank you once again for your continued support.

Ngā mihi nui,

Al Bramley

Chief Executive, Zero Invasive Predators

An encounter with 27 kea in the Perth River valley, April 2020

May 11, 2020

The ZIP field team returned to work in the Perth River valley on Tuesday 28 April, shortly after the COVID Level Four restrictions were lifted. Our field ranger Mike and his possum detection dog Pepper spent their first night back in the field camping by the headwaters of the Barlow River, where they were tasked with tracking down a possum we had detected in our network of lured trail cameras.

The following morning they awoke at 5:00am to a tell-tale cacophony of shrieks and an ominous rustling. They dragged themselves outside, and were shocked to find their ultra-hardy canvas storage bags and dry bags chewed to ribbons, gear strewn about the campsite, and several juvenile kea engaged in a serious attempt to dismantle their tent.

It’s normal for our team to camp in single-person tents, with some gear stored outside the tent, packed in dry bags and thick canvas storage bags to protect it from weather and the odd curious kea. While there have been a few minor instances of kea interfering with gear at other locations in the Perth River valley, we have never experienced such a targeted, sustained attack at this particular campsite!

Some of the gear in question. Not pictured: an electronic rifle scope that will probably never be seen again!

While Pepper watched from a safe distance, shaking ‘like a fish’, Mike counted an incredible 27 birds at the tahr camp, and caught the encounter on video (see below). Then, man and dog gathered what was left of their field gear and made a hasty retreat to the nearest bivvy.

The large number of young kea seen during this encounter coincides with the end of the fledgling season (November to May), a time when all juveniles from the previous breeding season reach independence. Although Mike and Pepper may not have been smiling at the time, a close encounter with such a large flock of juveniles is a very positive sign, and we are delighted by the frequent kea sightings reported by all of our field rangers. Along with the results of our recent kea survey, we are seeing increasing evidence that the Perth River kea population is thriving as we work to protect the site against possums, rats and stoats.

Kea survey in the Perth River valley, March 2020

April 21, 2020

On Wednesday 18 March, ZIP worked with several members of the South Westland community to conduct a kea survey in and around the Perth River valley field site. The purpose of the survey was to provide additional information to help us more confidently estimate the effect of our 2019 predator removal operation on the local kea population.

Background

ZIP has been working in the Perth River valley since early 2018. At this site we are testing and refining an approach to completely remove possums, rats and stoats from large areas, and then prevent them from re-establishing, for the long-term, sustainable protection of native species such as kea.

When we began work in the Perth River valley, experienced kea catchers spent three days banding kea within the field site. During this work, they caught and banded 55 kea, and estimated a total population of 75-100 kea within the area.

In autumn/winter 2019, we carried out an initial predator removal in the 12,000 ha field site using a modified technique for applying aerial 1080. While we anticipated that the complete removal of predators would have significant long-term benefits for kea in the valley, we recognised the need to mitigate any potential risks to kea that this modified technique might present. In the months leading up to the predator removal operation, we worked with DOC and the Kea Conservation Trust to develop and deploy two new methods to protect kea during the operation (alongside a range of more standard risk mitigation measures that were already in place).

Prior to the operation, we exposed kea to non-toxic baits that mimicked the look and smell of toxic baits, containing the bird repellent anthraquinone. This bait was used to train kea to avoid cereal baits.

To attract kea to these aversion baits, we also placed tahr carcasses (repurposed from tahr control operations) at several sites above the altitudinal boundary of the operational area.

Our research confirmed that tahr carcasses are highly attractive to kea, and capable of drawing groups of kea to specific locations within the field site. So, in winter 2018, we field trialled the use of trail cameras lured with tahr carcasses to survey kea at several alpine locations within the site. The images gathered from this network of cameras suggested a similar population to the kea catchers’ estimate.

In late 2019, after we had completed the predator removal operation, we carried out another survey using camera traps lured with tahr carcasses, to help us understand the effect of the operation on the kea population. The numbers of kea seen on camera during this work were similar to those seen in winter 2018, suggesting that the initial impact of our predator removal operation on the kea population was likely to have been small.

The March 2020 survey

The March 2020 survey was carried out at eight locations (marked as blue dots on the map below) in and around the Perth River valley field site. Tahr carcasses were used to attract kea to each of the survey locations.

We were grateful to be supported on the day by Kaylyn and Marcus Pinney (Te Taho Deer Park/ New Zealand Deerstalkers Association), Ashley Cassin (Chair of the Glacier Country Tourism Group), Cliff Goodwin (Glacier Valley Eco Tours) and Su Sinclair (Project Support Manager, Predator Free 2050 Limited). Gus Gordon (Glacier Country Helicopters) helped us select the survey locations and place the tahr carcasses.

*One of the eight alpine locations at which kea were surveyed (Joseph Arand)*

At each of the survey locations, we worked with Kaylyn, Marcus, Ash, Cliff and Su to conduct five hourly kea counts, between 7:30am and 11:30am. Each time a kea was counted, we noted whether it was on the tahr carcass itself, or simply perched nearby. We also recorded any banded individuals we were able to identify, and synchronised the counts to minimise the chance of double counting birds.

*A group of four kea photographed during the March 2020 kea survey (Briar Cook)*

Over the course of the survey, between 25 and 39 kea were counted at the beginning of each hourly period (or an average of 30 per hour). This rate of sightings is similar to the rate at which kea were photographed by our trail cameras before the predator removal operation, and suggests that the number of kea now living in the valley is unlikely to have changed.

“It was a great experience to head up on the kea observation trip alongside Cliff Goodwin (owner/operator Glacier Valley Eco Tours). We were in an amazing spot and observed a good population of kea on our hourly inspections. With multiple locations observed at the same time, it was interesting to see the large numbers of kea that were present at certain sites.”

— Ashley Cassin, Franz Josef Glacier Hotpools

“It was interesting to discuss the ZIP program with [Science and Technical Ranger] Briar, and the ambitious nature of their plans. Being on the ground we could appreciate the scale of the area and how well the team has done to get the possum numbers down to just 3 animals. We appreciated the opportunity to see what is happening and we look forward to seeing how the project goes in the coming years.”

— Marcus and Kaylyn Pinney, Te Taho Deer Park/ New Zealand Deerstalkers Association

*A juvenile kea spotted during the March 2020 kea survey (Marcus and Kaylyn Pinney)*

Along with the many kea sightings our rangers enjoy while going about their work, helicopter pilot Gus Gordon’s recent estimate of 100-200 kea (based on the large numbers he has spotted while placing tahr for our survey and risk mitigation work), and the large collection of images captured by our trail cameras (including the one below), the results of this survey make us confident that there has been little change to this population.

*A group of six juvenile kea caught on camera at a tahr carcass in August 2019*

The relatively large population of kea in the valley can likely be attributed in part to a long history of predator control in the area. DOC has carried out five aerial 1080 operations here since 1997, which will have given several generations of kea an opportunity to breed successfully. Another factor is that these kea have had access to an abundance of nutrient-rich food in the form of tahr carcasses left by trophy hunters and by DOC’s tahr control operations.

The continued strong population of kea also suggests that the combined use of aversion bait and tahr carcasses has been largely successful in mitigating risks to kea from ZIP’s predator removal operation.

Seeing a healthy population of kea in the Perth River valley a year after our predator removal operation is hugely rewarding. We expect this population will continue to flourish as we learn to maintain an area free from the impact of possums, rats and stoats.

“The work ZIP’s doing in the Perth River valley is really necessary to help protect kea. These birds are intelligent, so we need to train them not to eat the baits while still getting rid of the rats, stoats and possums. ZIP has put a lot of work and thought into reducing risks to kea from 1080, and it’s been bloody awesome to see so many kea in the valley a year after their operation.”

— Gus Gordon, Glacier Country Helicopters

Zero Invasive Predators (ZIP) and COVID-19 – a letter from our Chief Executive

March 31, 2020

Kia ora,

I hope this finds you and your loved ones safe and adjusting to our collective new 'normal'.

Now that we have settled into our new work environments for at least the next four weeks, I wanted to let you know the status of the Zero Invasive Predators (ZIP) team and our programme of work.

All of the ZIP team members are now working from either their usual residences in Wellington, Christchurch and Hokitika, or staying with family members in other parts of the country. We are all in regular video, internet and/or phone contact with one another.

Almost all biosecurity and conservation work has ceased on public conservation land (with the exception of some offshore islands) and, consequently, our programme of work in the Perth River Valley is on hold. Likewise, trials at our Lincoln predator behaviour facility are also on hold, although we are continuing to look after the resident possums, rats and stoats.

While our field work and trials are on hold, we are well placed to stay busy and productive during this period. Disruptions to the planned programme of work are not unusual in our context, and the ZIP team is well set up to cope with change. We also know that each disruption also represents an opportunity to review and refine our work programme, and perhaps to even catch up on some overdue tasks. You may remember that our predator removal operation in the Perth River Valley was scheduled to be carried out in 2018, but delayed until the following year by weather conditions and heavy snow. We took this opportunity to develop and test new techniques to mitigate risks to kea, and then deployed these alongside the operation when it was eventually carried out in 2019. Another year on, and we are pleased to see a healthy population of kea living and breeding within the field site.

Over the next few weeks our team will take this current opportunity to complete a range of tasks including writing up and publishing research results, analysing the immense database of images acquired through our network of trail cameras, ensuring we are ready to continue developing our new predator detection camera when supply chains re-open, checking and maintaining our field supplies, reviewing and refining our programme of work, and refining and developing our internal administrative systems. For those of you running landscape-scale predator free projects, we are just a phone call away (although we are currently unable to supply products).

We will continue to notify you as soon as possible about any significant developments that affect our programme of work, and for some of you, seek your continued input into planning the work and your advice on how we can deliver it. Please don’t hesitate to contact us if required.

In the meantime, I’d like to wish you and your families all the best over the coming weeks.

Al Bramley
Chief Executive, Zero Invasive Predators

Update on Perth River valley work programme – response to isolated rat breeding

January 7, 2020

Tuesday 7 January 2020

In late July 2019, Zero Invasive Predators (ZIP) completed a predator removal operation in the Perth River valley, South Westland. This operation is part of a research and development project that aims to test and refine the ‘Remove and Protect’ approach for the complete removal of possums, rats and stoats from large mainland areas, and subsequent protection of these areas against predator re-establishment. The research area covers 12,000 hectares.

Since the operation, we have been using our network of 147 trail cameras paired with MotoLure automated lure dispensers and approximately 3,000 chew cards lured with peanut butter to detect any remaining possums, rats or stoats.

By mid-November, just 3 possums and 5 rats had been detected within the area – and no stoats. We established a small network of traps and extra cameras at the site of each rat detection, and caught 4 rats.

In mid-December 2019 we discovered evidence that localised rat breeding had occurred after the predator removal operation, across a small ‘footprint’ of approximately 50 hectares. We’ve always anticipated that the Remove and Protect approach will require a range of techniques to respond to animals that survive a predator removal operation or reinvade an otherwise predator-free area. Given the nature of the terrain, the only feasible response to remove this emerging population and prevent rats from re-establishing in the valley is to carry out a small-scale aerial ‘spot treatment’.

Consequently, today we applied non-toxic cereal prefeed bait (at a rate of 1kg/ha) across the 50 hectare footprint and a surrounding buffer zone. When the weather conditions next allow, we propose to apply a single application of 1080 bait (at a rate of 2kg/ha) over the emerging rat population footprint.

The location where bait is applied will be displayed on the DOC Pesticide Summaries website, and on a map accompanying the signage within the project area itself.

Image credit: Ngā Manu Nature Images, 2007

Updates