After six years of no reported mynas on Ātiu, the Natural Heritage Trust is declaring its Eradication Project a success. The removal of a population of about 6000 mynas made it the world’s largest myna eradication on an island. It dwarfed the second largest island-eradication of 1641 mynas on North Island in the Seychelles completed in February 2019. By Gerald McCormack, Cook Islands Natural Heritage Trust.

The eradication was requested by the Ātiu Island Council; and the seven-year project was implemented with funds from Critical Ecosystem Partnership Fund (CEPF) of Conservation International, together with extensive in-kind contributions from Air Rarotonga and Atiu Villas.

The Natural Heritage Trust led an international team to reintroduce 27 Kura (Rimatara Lorikeets) to Ātiu in April 2007. The first Kura nest was found in August 2008, and the first fledgling to emerge was knocked to the ground by two mynas. It recovered and flew up into a coconut palm where the mynas knocked it to the ground again. It was protected by observers until it was reunited with its parents.

Mynas are well-known for harassing our landbirds. However, the threat to the small population of reintroduced Kura was an unacceptable risk. The decision was made to reduce the number of mynas to lower the level of harassment.

The Reduction Project
The Reduction Project started in May 2009 using the avicide Starlicide^TM (DRC1339), a slow-acting coma-inducing toxin for birds, delivered in boiled rice which was not attractive to any of the native birds. The first experiment involved placing the baited rice on a sheet inside a large cage with mesh to allow myna entry while excluding feral chickens, which might have been killed by eating the toxic rice. The test was near a roost, and many mynas fed inside the cage before retiring to the roost.

The expectation was that most mynas would become unconscious and die sometime during the next two days, and that survivors would not suspect that the free-rice evening meal was the cause of their demise. Instead, many mynas fell to the ground before dawn and birds missing partners when they dispersed in the morning caused chaos. During the day, dead mynas were widespread on the inland. That evening, mynas returned to the roost but none visited the free-rice restaurant.

It was concluded that Starlicide^TM could kill more rapidly than expected, and when used near a roost the birds did detect the source of the problem. A most unexpected outcome was that a small chicken that fed on the toxic rice with the mynas was present and feeding alone the next evening. This demonstrated that the particular avicide was not a threat to feral fowls.

As a result, the large cumbersome cage was abandoned, and poisoning moved to laying toxic rice on freshly cultivated ground, on opened fruits, on bread, and on mobile trays. Of the methods, the mobile trays became the system of choice. The poisoning was undertaken several times a week by George “Birdman” Mateariki with the support of Maara Akava, who were paid a per diem.

At the same time in May, the Trust provided a thesis topic for Jess Mitchell of Leeds University to research the number of mynas on Ātiu using roost-counts and road-transect counts. In finding the roosts, Jess was aided by the students of Enuamanu School, who found 38 roosts for which they earned $900 for the school. All the roosts were in the inland volcanic area of the island, spread over an area of about 11,000 hectares.

Jess found that the roosts averaged about 182 mynas giving a total of about 6933 mynas +/-1528. Somewhere between 5405 and 8460 mynas. The Trust then undertook repeated road counts through the adjoined villages to obtain an average count to represent a population of 6000 mynas as an encouraging “starting population”. The author regularly surveyed the birds in the villages to estimate the success of the project. The birds killed by poisoning were widespread and their numbers were estimated from the author’s population counts.

With George and Maara poisoning, we also encouraged the community to participate by trapping mynas using their traditional fowl traps. We provided free wire-mesh for the construction of many more traps, and the bounty payments started at NZ$1 per right-foot delivered to paymaster, Roger Malcolm at Atiu Villas. Bounties rose to $2 and then $4.

Over the next 18 months, local trappers, actively supported by George, produced 1300 right-feet for bounty payouts of NZ$2900. However, by August 2010, the mynas were very wary of local traps and most trappers abandoned the activity. We also provided two pellet guns and while a few residents found them useful, shooting mynas proved more difficult than expected.

During the first six months, to December 2009, the poisoning killed an estimated 4138 mynas, reducing the population to about 2000, but over the summer breeding season numbers increased up to about 3500 mynas. (See the summary graph.) During 2010, George again poisoned a lot of mynas, and by September we concluded that the Kura had clearly increased. The Reduction Project had served its purpose and it was concluded it should be terminated.

The Eradication Project
Before announcing the termination of the Reduction Project to the Island Council, I had heard that they intended to ask for an Eradication Project. Unfortunately, this would be declined, because local trapping had been abandoned and poisoning alone would never eradicate the myna.

In October, with Council approval, we had Jason Tuara, an experienced hunter from Rarotonga, compare shooting mynas with a silenced .22 and a noisy 12ga shotgun. After one day it was concluded that the .22 was very inefficient. During the next few days Jason shot about 60 mynas a day with the shotgun, and a few residents objected to the way their pigs were disturbed by the noise.

While poisoning and shooting together might have enabled the myna to be eradicated, we did not think it would be an option because the Council would not approve the use of noisy, socially disruptive shotguns beyond the test. How mistaken we were.

The Council made it clear that the myna was a very serious pest on the island because of the mess it caused in and around houses, the widespread damage in the fields to ripening fruit and because it harassed nesting native birds, especially the Kūkupa (Cook Islands Fruit-dove) and Ngōtare (Chattering Kingfisher), along with the recently reintroduced Kura.

The Council wanted the myna gone, and they approved the use of shotguns by Jason on a system of pre-announced location information. Before each visit, maps were displayed in each village with the inland beyond the centralised villages divided into six radiating sectors and showing which sector would be occupied by the shooter on each of the six days of shooting. After a week of Armageddon, there would be three or more weeks of peace, before the noise returned.

The radiating sectors were centred on the food-rich valleys which enabled growers to avoid a particular valley for the day it was occupied by the shooter. In the early days mynas were so abundant that shooters would blast dozens of times a day, and the noise echoed up the valleys into the villages. We were continuously ready to terminate the project. The tolerance of the community was a measure of how much the myna was loathed.

During the first six months, to mid-2011, Jason shot 1800 mynas at a rate of about 64 per day. He then had a time of other commitments so we advertised for more professional “Bounty Hunters”. This led to successful separate visits by Rarotonga shooters Dan OBrien, Dave Tuoro and Kevin Greaves.

After two years of shooting, to the end of 2012, the shooters had killed 8350 mynas, yet the estimated population persisted at 1500 to 2000 birds, falling during the non-breeding season and rising again after each breeding season.

It was increasingly obvious that poisoning and shooting could not eradicate the myna on Ātiu.

From poisoning to decoy trapping
I had followed the career of the Spanish myna trapper Susana Saavedra for a couple of years and had the opportunity to meet her on Tahiti in December 2012 where she was trapping mynas that were harassing the endangered ‘Omama‘o (Tahiti Flycatcher). She showed me the large, British square trap with a drop door on each side and top access to the decoy myna in a central compartment. She was having a lot of success on Tahiti.

The Trust copied her traps and in January 2013 she came over from Tahiti for three weeks to demonstrate their use and how to maintain the decoy birds. The decoys were very successful in attracting other mynas to the traps and overnight George moved from master poisoner to master trapper with decoys.

The Trust redesigned the British trap to make it much smaller and easier to service at night by placing paired doors at each end along with side-access to the decoy bird. George, assisted by his wife Barbara, spent several nights a week setting traps during the evening. It was an immense task, and in addition they had to maintain healthy decoy birds.

Approaching the traps at night in torchlight was always a time of expectation, and great excitement when it contained four mynas – a “full house!”. During the first six months of 2013, George and Barbara trapped 1200 mynas, averaging 200 a month, and this dropped to 630 mynas (105/month) for the next six months. The going was getting tougher. By mid-2014, 20 mynas trapped in a month was a good month.

During 2014 shooting also became exponentially more difficult as mynas became scarce, and increasingly secretive and wary. In August, for inspiration, we brought Susana back for a month and she showed how the decoy in a trap could also be used to attract free mynas to poison baits near the trap. Overall, she was very disappointed at the catch rate.

George persisted with trapping despite the low capture rate, and Jason, assisted by local shooter Toru Orii, spent hours tracking dressed in camouflage and using pre‑recorded myna songs. Shooting two was a good day, and four an excellent day.

By mid-2015 Jason had shot 6625 mynas during 335 days, while the other shooters during 120 days had taken out 3868 mynas for a grand total of 10,493 mynas.

In November 2015, George trapped what were thought to be the last two mynas. Dissection revealed they were both female, which was consistent with earlier evidence that when a shooter had to take one of a wary pair it was inevitably the male.

In early 2016, Jason visited for nine days of searching and found no mynas. It seemed that the mynas were finally gone. And, George had the long-deserved honour of taking out the last birds.

However, it was not to be. In May 2016, two very elusive mynas were reported in the area of Araki, and they were reported again in August. Jason came back in September and after several days of tracking he shot four mynas in the extended area around Araki. The three recovered birds were females. The extreme elusiveness of the birds indicated they were local mynas rather than recent arrivals.

The payout to shooters rose in relation to the increasing difficulty of the task. In 2010 they shot about 65/day at NZ$5 each; 2012 about 42/day at $8 each; 2014 four per day at $148 each; and in 2016, Jason’s four mynas earned $1070 each!

Another measure of the increased difficulty of removing the mynas is shown in the graph of the number removed each year. During the first three years 7059, 5250 and 6019 were removed. For 2013 there was a definite drop to 3594; and the population collapsed in 2014 with 650 killed. 2015 saw a mere 75 removed, and finally in 2016 the last four were shot.

Two very elusive mynas were reported around Araki in April 2018. It was decided they were probably females and no action was required unless there was evidence of breeding. They were never reported again.

It was decided that after five years of no reported mynas on Ātiu, we could safely conclude the eradication had been successful. And here we are after six years of no reported mynas, declaring the eradication a success.

The world’s largest eradication
The Ātiu Myna Eradication Project has been the world’s largest successful eradication on an island based on the original population of 6000 birds. The seven-year project to the end of 2016 killed about 27,000 mynas on a heavily forested island of 2900 hectares, although almost all the birds were in the inland area of about 1100 hectares. The extensive forests made finding mynas difficult, especially towards the end of the project.

The cost of the eradication was about NZ$270,000, or NZ$11-per-myna for all birds killed, or NZ$45-per-myna based on the initial population of 6000 mynas. About 70 per cent of the funding was aid from Conservation International to the Trust, with most of the rest as in-kind contributions from Air Rarotonga and Ātiu Villas, in donated flights and accommodation. Roger was the volunteer leg counter and pay clerk on Ātiu, and the main on-site cajoler. Important emergency and bridging finance was provided by Natural Heritage, BirdLife International, Te Ipukarea Society and the National Environment Service.

The world’s second-largest myna eradication programme was completed in February 2019 by trapping and shooting. It removed 1641 mynas from North Island in the Seychelles. North is about 201 hectare or 7 per cent the size of Ātiu or 18 per cent of the inland of Ātiu. The cost of the North Island project was about NZ$201,200 or NZ$123-per-myna. (Feare et al. 2021)

Would mynas re-introduce themselves to Ātiu? This is very unlikely. Mynas were introduced to Ātiu and Ma‘uke in 1915 and 1916. During the following century they never colonised Miti‘āro, which is 40km and 45km distant, respectively. Ma‘uke is 77km from Ātiu, which make a natural reintroduction very unlikely, although a cyclone could make a mockery of this conclusion.

Three good outcomes
The eradication of the myna on Ātiu has dramatically changed the quality of life. No longer is there a myna mess in and around homes, fruits are ripening naturally without myna damage, and everywhere native birds have a high visibility.

One bad outcome
The myna was introduced by the Government to the outer islands in 1915 and ’16 as a biocontrol to reduce the impact of the Coconut Stick-insect, ‘Ē‘ē or ‘Ē on the supply of coconuts for copra.

The stick-insect had a tradition of causing periodic plagues that severely damaged palms by eating the leaflets. They are nocturnally active, mainly on the underside of leaflets. Plantations had a spacing of eight yards and the flightless female stick-insects could spread from crown to crown.

When the project started most coconut palms on Ātiu were healthy regardless of their age, and the island had a small industry of exporting intact coconut fronds for thatch. During the Eradication Project stick-insect damage remained minimal through mid-2011 but showed a dramatic increase in early 2012.

At that stage it was estimated there were still about 2000 mynas on the island which showed that the effective control of the insect required a very dense population of mynas. The hope of some residents that the island could have a small, non-nuisance population of mynas to effectively control the ‘Ē‘ē, was doomed.

We could have stopped the eradication at that point, but after consultation with the Council it was decided to continue. And, if eradication was achieved, then to wait a few years to see if a natural harmony developed between the presence of the stick-insect and the maintenance of enough healthy palms to supply coconuts for food, and fronds for mulch on Taro patches.

In the meantime, the community realised it is the oldest palms that were most damaged, especially in the old plantation around the harbour. Even there the palms mainly went through a dieback-recovery cycle, and gradually the community has been planting new palms with greater spacings.

Clearing away weeds under palms has also proved effective. This is because the flightless females live entirely in the crowns of palms with their eggs falling to the ground to develop and hatch. The hatchlings rely on the protection of the weeds while they grow large enough to climb to the crown of a nearby palm. Clearing the weeds promotes the death of the young stick-insects through desiccation, trampling by livestock and harvesting by chickens.

• NEXT WEEK: War of the wings: The Rimatara lorikeet and how I learnt to hate the Atiu mynah