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Conservation of kakerori (Pomarea dimidiata) in the Cook Islands in 2004/05

Available Online

Robertson Hugh A

Saul Edward K

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 250300 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.

Conservation of kakerori (Pomarea dimidiata) in the Cook Islands in 2006/07

Available Online

Robertson Hugh a.

Saul. Edward K.

In 1989, the kakerori (Pomarea dimidiata) was one of the 10 rarest birds in the world with a declining population of just 29 individuals living in forested hill country in the Takitumu Conservation Area (TCA) of south-eastern Rarotonga, Cook Islands. Following 12 years of rat poisoning, the population had increased to 255 birds in August 2001. The programme then shifted from species recovery to sustainable management of the Rarotonga population at 250 to 300 birds. The rat poisoning effort was reduced, and an insurance population was established on Atiu. By August 2004, following the reduction of poisoning from weekly to fortnightly, and the transfer of 30 youngsters to Atiu in 200103, there were 281 birds on Rarotonga and 25 on Atiu. The southern Cook Islands were hit by five tropical cyclones in a four-week period in FebruaryMarch 2005, and forests on Rarotonga were severely damaged. Kakerori survived the storms remarkably well, but the main effect was observed in the following breeding season (2005/06), when nesting success on Rarotonga was exceptionally poor. Reduced canopy cover caused nests to be exposed to abnormally wet conditions, and lack of fruit meant that rats were exceptionally hungry. Only 31 yearlings were known to be alive in August 2006about half the expected numberand annual mortality of banded birds (25%) was the highest since management began. The kakerori population on Rarotonga fell 8% from 275 birds in August 2005 to a minimum of 254 birds in August 2006. The situation was better on Atiu, with the population growing from about 32 adult birds in 2005/06 to a minimum of 37 adult birds in 2006/07, and an Atiu-bred pair nested successfully for the first time. The 2006/07 breeding season on Rarotonga was moderately successful, with a minimum of 51 fledglings found. Because the sustainable management regime of fortnightly rat poisoning in the TCA was only just adequate in giving protection to adult kakerori, the annual poisoning programme was modified by adding rounds of interim poisoning in April and July 2007 aimed at reducing rat and cat numbers before the breeding season.

Eradicating rats from Maninita Island, Vava'u, Kindgom of Tonga

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Houston D.M.

In June/July 2002 an eradication programme to remove Pacific rats from Maninita Island in the Vava'u group of the Kingdom of Tonga was initiated. The techniques used were similar to those used in successful rat eradications in New Zealand, in that Pestoff 20R pellets and a network of bait stations were used. Conditions on the island were not what was expected, the forest having been adversely affected by cyclone Waka and subsequent defoliation by caterpillars, resulting in an open forest canopy. Rats were found to be present on the island in high numbers and were breeding. At this stage it appears that the operation was successful, as no rats were caught in monitoring trapping after 20 days of operations, although follow-up monitoring needs to be carried out in late 2002 to confirm this. There appears to have been no negative impact on non-target species.

Rat eradication on small islands in the Vava'u group, Kindom on Tonga

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Houston D.M.

In June/July 2002 the eradication of Pacific rats from Maninita Island in the Vava'u group of the Kingdom of Tonga was attempted using Brodifacoum pellets in bait stations. In December 2002, Maninita was revisited and rat trapping carried out to determine if rats were present. While no rats were caught and none were seen, further monitoring in June 2003 is recommended before the island is declared "rat free '. Using the same techniques used on Maninita, the eradication of rats on neighbouring Taula and Lua Loli was attempted. Despite poor weather delaying rebaiting visits to the islands, the operation thus far appears successful. Permanent bait stations set up on Maninita to minimise the risk of rats re-invading the island were found to have been tampered with and evidence of booby chick harvesting was seen on Taula. Regular visits to the islands to maintain bait stations and maintain a presence are recommended.

Notes on the verterbrate fauna of Tongareva atoll

Island and Ocean Ecosystems, BRB

Available Online

Clapp Roger B

At the time of the POBSP visit, cats (Felis domestica), dogs (Canis familiaris), and pigs (Sus scrofa) were being raised by the natives. Comments in Ward (1967) and by Lamont (1867) suggest that the pigs may have been introduced to Tongareva in 1853 from the ship wrecked vessel Chatham. Rats (Rattus sp.) were numerous in 1965, but as no specimens were collected their identity is unknown. Lamont (1867) stated that in 1853 "... [the natives] had never seen an animal larger than a very small rat, that lives principally in the cocoa-nut trees " Lamont's description suggests that the rats on Tongareva are Rattus elegans, a species widely distributed on the Pacific Islands.

Systematics and ecology of the land crabs (Decapoda: Coenobitidae, Grapsidae and Gecarcinidae) of the Tokelau Islands, Central Pacific

Island and Ocean Ecosystems, BRB

Available Online

Wodzicki Kasimierz

Yaldwyn J.C.

The Tokelau Islands consist of three atolls (Atafu, Nukunonu and Fakaofo) approximately 500 km north of Western Samoa. Their numerous islets are formed mainly of coral sand and rubble with no standing freshwater. Sixty-one plant species have been recorded, 13 of these being introduced and 10 being adventives. There are three vegetation zones, the beach, the beach-crest, and the interior coconut/fern zone with the physiognomy of a humid tropical forest. Marine invertebrates have not been studied. One hundred and fifty insect species in 83 families have been recorded with most being widely distributed South Pacific species including several introduced agricultural pests, e.g. Rhinoceros Beetle. Some marine fishes have been listed and 7 species of lizards are known from the group. Twenty-six bird species (15 sea birds, 8 shore birds and 3 land birds) are known but none are endemic races. Domestic pigs, cats, man and the Polynesian Rat (Rattus exulans) are the only mammals. R. exulans is an economic pest as it causes considerable damage to the coconut crop and assists in the spread of filariasis.

Distribution of rat species (Rattus spp.) on the atolls of the Marshall Islands: past and present dispersal

Island and Ocean Ecosystems, BRB

Available Online

Spennemann D.H.R.

The study of dispersal processes of small mammals, and especially of rodents, has a wide range of applications and until recent years there were few publications discussing the colonisation of 'oceanic' islands by small mammals (cf. Crowell, 1986; Diamond, 1987; Hanski, 1986;Heany, 1986; Lomolino, 1986). This essay will be concerned with the distribution of rat species in the Marshall Islands and its implications on the interpretation of the settlement and human use of the atolls. It will be argued that in all instances the introduction of rats was caused by people and that accidental transport, such as rafting on drift wood and the like, is as unlikely as introduction by means of ship wrecks. Human transport as well as the rats' own inability to cross great distances of water makes them bad zoogeographical markers, as already pointed out by Braestrup (1956), but it is precisely this trait that is of concern here. This paper will argue that the Polynesian rat (Rattus exulans) was an intentional introduction to the area and that its distribution throughout the Marshall Islands was a deliberate strategy.

Atolls as settlement landscapes: Ujae, Marshall Islands

Island and Ocean Ecosystems, BRB

Available Online

Weisler Marshall I

Williamson and Sabath (1982) have demonstrated a significant relationship between modern population size and environment by examining atoll area and rainfall in the Marshall Islands. The present work seeks to extend that argument into prehistory by examining the relationship of ancient habitation sites and size of aroid pit agricultural systems to atoll land area and rainfall regime along the 1,500-3,500 mm precipitation gradient in the Marshall Islands. Four atolls were selected for study: Ebon at the wettest extent in the extreme south; Ujae and Maloelap near the center of the archipelago; and Utrok at the dry north. The first phase of this long-term archaeological program is reported. During the survey of Ujae Atoll (90 05' N, 165° 40' E), three habitation sites, an aroid pit agricultural zone, one early historic burial, and seven fish traps, weirs, and enclosures were recorded. Along with excavations at two habitation sites (8 m2 total area), 35 traditional artifacts were recovered (shell adzes, ornaments, and manufacturing tools). Seven radiocarbon age determinations document land use beginning as early as the third century A.D. A beachrock sample dated to 2450 ± 70 BP relates to atoll development. Some 4,748 bones of fish, birds, turtles, Pacific rats, lizards, humans, and possible cetaceans, along with nearly 13 kg of shellfish, provide the basis for understanding prehistoric subsistence, human adaptations to the atoll setting, and land use patterns.

Pohnpei rat eradication research and demonstration project, Pohnpei, Federated States of Micronesia, 16 January - 7 March 2007

Available Online

Wegman, Alexander et al.

Through the Pohnpei Rat Eradication Research and Demonstration Project, The Conservation: Society of Pohnpei (CSP), Island Conservation (IC), and the Pacific Invasives Initiative (PII) are working together to enhance the biosecurity of Pohnpei's island ecosystems, and that of other similar ecosystems throughout the Pacific. This research and demonstration project will help NGO and government conservation organizations develop the capacity to plan. fund, and implement subsequent: rat eradications in threatened island ecosystems. CSP, IC, and PII also partnered with the following organizations to cany out this pioneering conservation project: the Pacific Invasives Learning Network, The Nature Conservancy, the Pohnpei State Government, the Micronesia Conservation Trust, Micronesians in Island Conservation, local government officials, and local landowners.

Rat damage to coconuts in the Gilbert & Ellice Islands / F.J. Smith

Smith, F.J.

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