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In 1989, the kakerori (Pomarea dimidiata) was one of the ten rarest bird species in the world, with a declining population of just 29 birds in the Takitumu Conservation Area (TCA) of southeastern Rarotonga. As a result of conservation management, the kakerori population rebounded, with up to 300 birds being recorded on Rarotonga and Atiu in 2004/05. The southern Cook Islands was, however, hit by five tropical cyclones over a 4-week period in February–March 2005, and much of the forest on exposed faces, spurs and ridges (traditional kakerori habitat) was severely damaged. The population survived remarkably well, with a minimum of 274 adults known to be alive in the TCA in August 2005. An additional 17 adults were found on Atiu between August 2005 and March 2006. The main\ casualties of the cyclones on Rarotonga appeared to be young birds (1–3 years old) and very old birds (> 20 years old). Because the population on Rarotonga remained well within the management target of 250–300 individuals, rat poisoning was again done fortnightly, as in the previous 2 years. Breeding productivity was exceptionally poor in 2005/06, mainly because of nesting failures or early fledgling deaths caused by abnormally wet conditions during the main fledging periods. Nests were more exposed to the elements because the cyclones had extensively defoliated the canopy. Furthermore, rats were often seen foraging during the day, apparently struggling to find food (few trees were fruiting). Only 22 fledglings were definitely seen in 2005/06; however, some territories were not checked or poorly checked during the breeding season, and some fledglings may have dispersed to better vegetated sites. We recommend that rat control should return to the weekly poisoning regime used during the 1989–2001 recovery phase of the kakerori management programme if the August 2006 census reveals that the population has fallen below 220 birds (a 20% decline from pre-cyclone levels). Otherwise the regime of the sustainable management phase (fortnightly poisoning) should continue.

In 1989, the kakerori (Pomarea dimidiata) was one of the ten rarest bird species in the world, with a declining population of just 29 birds living in south-eastern Rarotonga. As a result of conservation management, the kakerori population has rebounded, with a minimum of 281 birds on Rarotonga and 19 birds on Atiu in summer 2004/05. Since 2001, the emphasis of management in the Takitumu Conservation Area (TCA) on Rarotonga has shifted from the ‘recovery’ of kakerori to ‘sustaining’ the population at 250–300 individuals. In 2004/05, all rat bait stations were filled fortnightly, and so the labour costs were reduced by 30% to 34 person days, and toxin use (57 kg of Talon®—active ingredient brodifacoum) was reduced 81% from the peak year during the ‘recovery phase’. Kakerori breeding productivity was unusually high in 2004/05 because several pairs raised two broods. In the poisoned area, apparent breeding success was significantly higher (1.35 fledglings/breeding territory) than in the unpoisoned area (0.55 fledglings/ breeding territory); however, this difference was at least partly due to more effort being spent searching for fledglings in poisoned areas. A minimum of 59 fledglings was detected in 2004/05; however, some territories were not checked during the breeding season, and then a series of five tropical cyclones struck Rarotonga in a 4-week period in February/March 2005, which halted our fledgling searches, and caused severe damage to some habitat in the TCA. We expect that many kakerori perished during these cyclones; however, the population on Atiu, which was only affected by two of the five cyclones, survived unscathed. These catastrophic weather events highlighted the vulnerability of single-island endemic birds, and underlined the value of establishing an ‘insurance’ population on Atiu. We recommend that the poisoning regime should return to that used during the ‘recovery phase’ of the kakerori management programme if the August 2005 census reveals that the population has fallen below 220 birds (a 20% decline), otherwise the recent programme of fortnightly poisoning should continue.

There are five toxicants (brodifacoum, bromadialone, coumatetralyl, diphacinone, and flocoumafen) registered for rodent control in New Zealand. They are all anticoagulants and are available in water-resistant bait formulations (i.e. wax coating, wax block, or egg). Several new rodenticide products, which are currently in the process of being developed or registered, including a new anticoagulant difethialone, have also been identified. There are no published data on the relative effectiveness, palatability, or durability of the existing rodenticides for field use under New Zealand conditions. However, relevant published information on laboratory and wild rodents is reviewed. It is concluded that the highest priority should be to assess the four weather resistant, second-generation anticoagulant products (Pestoff® Rodent block, Talon® 50WB, Contrac®, and Baraki®) for palatability, durability, and effectiveness for an island protection situation. Improvements could then be made to the existing products if required with additives to improve palatability or durability, lures to attract rodents, and repellents for non-target insect, lizard and bird species. Trials of an alternative (e.g. cholecalciferol) to the persistent anticoagulants should also be considered for island protection. The most rodent-attractive bait station which also eliminates bird access needs to be determined for the complete island protection system.

This is the final report describing the results from the second and third years of a three-year programme to determine the costs and benefits of aerial 1080 possum control operations to North Island robins (Petroica australis longipes) and moreporks (Ninox novaeseelandiae) in Pureora Forest Park, North Island, New Zealand. During this study robins were individually colour-banded, and moreporks radio-tagged in both treatment and non-treatment study areas. A poison operation using carrot baits in August 1997 covered 8577 ha and incorporated the 300 ha Waimanoa study area. A poison operation using cereal baits in August 1998 covered just the 200 ha Long Ridge study area. After the 1997 operation, very few possums remained alive and rat foot-print tracking indices remained very low during the robin nesting season (September 1997 February 1998). Similarly, possum and rat population indices were much reduced after the 1998 operation, but rats and possums were found in a small portion of the study area, presumably because it did not receive baits. Following both the 1997 and 1998 poison operations, there was no significant difference in the proportion of banded robins that disappeared from the non-treatment and treatment study areas. During the 1997/98 nesting season, the nesting success of robins was significantly better in the treatment area than in the non-treatment area. One year after the poison operation (spring 1998), the robin population in the treatment area had increased by 37% on the number present just prior to the poison operation, compared with 16.3% in the non-treatment area. No radio-tagged moreporks were available in the treatment area during the 1997 poison operation, and all three radio-tagged in each of treatment and non-treatment areas were still alive two months after the poison operation in 1998.

Kiore were eradicated on Double Island using two different methods. The larger islet was treated with one manual application of STORM 4 g wax block rat baits containing 0.005% by weight Flocoumafen, in October 1989. The smaller islet received one application of toxic kibbled maize (0.005% bromodialone by weight) after 4 nights prefeeding in November 1989. Kibbled maize was dispensed in silos. No sign of kiore has since been found during four visits to both islands. The cost per hectare for both methods were quite comparable. The nett cost for eradication on the larger islet (19 ha) was $310/ha, the smaller islet cost $432/ha. Both methods are considerably cheaper than the technique used to eradicate Norway rats (R. norvegicus) from Hawea Island. For future rodent eradication campaigns it is suggested that aerial applications of poisons may be made on all islands greater than 50 ha, and that size should be no barrier to rodent eradication. However, substantial non-target have been recorded when 1080 baits were broadcast aerially to control possum. Non-target kills of a similar magnitude may be experienced on larger and more sensitive islands.

The Department of Conservation, West Coast, requested Manaaki Whenua - Landcare Research, Lincoln, to test the effectiveness of two ultrasonic devices, Transonic ESP and Yard Gard, for repelling captive stoats (Mustela erminea) from a food source. If they repelled stoats, ultrasonic devices could be used to protect nesting birds such as kiwi (Apterygiformes), penguins (Sphenisciformes), and petrels (Procellariiformes) and their eggs and chicks from predation.