Recovery of the Kakerori: An Endangered Forest Bird of the Cook Islands

Robertson, Hugh A.; Hay, J. R.; Saul, Edward K.; McCormack, Gerald

doi:10.1046/j.1523-1739.1994.08041078.x

Cited by 45 publications

(48 citation statements)

References 13 publications

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“…Bird demographic responses to predator removal programs 3851 Robertson et al (1994) and Robertson and Saul (2007) Mean ± SE (all studies) 0.33 ± 0.02 0.59 ± 0.02…”

Section: Discussionmentioning

confidence: 99%

Bird demographic responses to predator removal programs

2010

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Invasive predators pose a significant risk to bird populations worldwide. Humans have a long history of removing predators from ecosystems; current island restoration actions typically focus on the removal of invasive predators, such as non-native rodents, from seabird breeding islands. While not overly abundant, the results of predator removal studies provide valuable information on the demographic response of birds, and can assist conservation practitioners with prioritizing invasive predator removal projects. We review such studies focusing on observed demographic responses of bird populations to predator removal campaigns and whether ecological factors are useful in predicting those responses. From the 800? predator removal programs indentified, a small fraction (n = 112) reported demographic responses of bird populations. Change in productivity was the most commonly reported response, which on average increased by 25.3% (2.5 SE) with predator removal. The best supported model for predicting the change in productivity from predator removal incorporated bird body mass, egg mass, predator type, nest type and an interaction term for body mass and nest type (AIC c weight = 0.457). The predicted percent increase in productivity resulting from hypothetical predator removal ranged from 16.9 to 63.0% (mean = 45.0, 5.6 SE), and was lowest for large, surface nesting birds such as albatrosses. The predicted increase in productivity resulting from predator removal alone was insufficient to reverse the predicted population decline for 30-67% of bird species considered, suggesting that in many cases, removal of predators must be performed in combination with other conservation actions in order to ensure a stable or increasing population.

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“…Bird demographic responses to predator removal programs 3851 Robertson et al (1994) and Robertson and Saul (2007) Mean ± SE (all studies) 0.33 ± 0.02 0.59 ± 0.02…”

Section: Discussionmentioning

confidence: 99%

Bird demographic responses to predator removal programs

2010

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“…In the mid 1800s, the kakerori was widespread and common on Rarotonga, however, the arrival of ship rats (Rattus rattus) led to a serious population decline (Robertson et al 1994). In 1989, the census size reached a low point of 29 known birds (including 13 females), but since then, intensive management based on rat poisoning in the 150 ha Takitumu Conservation Area, set up to protect this and other native species, has helped the kakerori population to recover rapidly to 250-300 at present (Fig.…”

Section: Introductionmentioning

confidence: 99%

“…In 1989, the census size reached a low point of 29 known birds (including 13 females), but since then, intensive management based on rat poisoning in the 150 ha Takitumu Conservation Area, set up to protect this and other native species, has helped the kakerori population to recover rapidly to 250-300 at present (Fig. 2;Robertson et al 1994Robertson et al , 2009Saul et al 1998). Since 1987, the kakerori population on Rarotonga has been monitored closely.…”

Section: Introductionmentioning

confidence: 99%

Genetic variation in the kakerori (Pomarea dimidiata), an endangered endemic bird successfully recovering in the Cook Islands

Chan

Robertson

Saul³

et al. 2010

Conserv Genet

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The Cook Islands endemic kakerori (Pomarea dimidiata) underwent a severe population decline following the introduction of ship rats (Rattus rattus) in the late 1800s. By 1989, the sole population on Rarotonga consisted of 29 known birds. Subsequent intensive management efforts enabled this population to recover to around 250-300 birds in recent years. This study, using microsatellite and mitochondrial DNA markers, assesses the level of genetic diversity and the genetic structure of the contemporary kakerori population on Rarotonga. No mitochondrial control region and cytochrome b haplotype diversity was found in the 11 samples examined at each locus. In 81 samples genotyped at 7 polymorphic microsatellite loci, an average of 4 alleles per locus were found, with an average observed heterozygosity of 0.65. No subpopulation division was found in this population. There was no evidence of inbreeding, but genetic bottleneck tests showed that the population had indeed experienced a significant genetic bottleneck. Recovery of the kakerori was successful in the past two decades despite low genetic diversity in terms of allelic diversity. Our data suggested that low allelic diversity did not hamper population expansion and the continued survival of this species, however, longer-term effects are still possible.

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“…Rarotonga (21°14 0 S, 159°46 0 W) is the largest and is a 'high volcanic island', reaching 653 m above sea level. Its approximately 10,000 inhabitants live on the narrow (\1 km wide) fertile coastal plain, whilst native forest covers the inland mountainous area (Robertson et al 1994). Atiu (19°58 0 S, 158°08 0 W) is a 'raised island' composed of an elevated coral limestone platform, known by the Polynesian name of makatea (Franklin and Steadman 1991).…”

Section: Study Areamentioning

confidence: 99%

Dispersal of fig seeds in the Cook Islands: introduced frugivores are no substitutes for natives

Staddon

Compton²,

Portch³

2010

Biodivers Conserv

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Across the Pacific, island vegetation is altering in response to changes in seed disperser assemblages brought about by extinctions and introductions of birds and other animals. On the Cook Islands in the South Pacific, the Pacific Banyan (Ficus prolixa, Moraceae) is undergoing little if any recruitment, possibly linked to a lack of dispersal agents. On Rarotonga, where F. prolixa is found in semi-urban and agricultural environments, there is no recent recruitment in contrast to the situation on Atiu where the tree is common in native forest. We examined the quality and quantity of seed dispersal offered to F. prolixa by the available frugivores on these islands, comparing the effectiveness of extant native and introduced species. The native Cook Islands fauna, particularly birds and bats, appear to be the most effective seed dispersers of F. prolixa, both in terms of quantity and quality. Whilst these are relatively numerous on Atiu, they rarely visit F. prolixa on Rarotonga. The native Chocolate hermit crab Coenobita cavipes is a previously unreported additional native seed disperser, conferring low quantity, but high quality dispersal. Introduced birds and mammals are the most numerous F. prolixa frugivores on Rarotonga and in non-forest environments on Atiu, but they act mainly as seed predators. Consequently, the losses and rarity of remaining native frugivores have not been compensated for by introduced species on Rarotonga which may be contributing to the absence of recruitment there.

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Recovery of the Kakerori: An Endangered Forest Bird of the Cook Islands

Cited by 45 publications

References 13 publications

Bird demographic responses to predator removal programs

Bird demographic responses to predator removal programs

Genetic variation in the kakerori (Pomarea dimidiata), an endangered endemic bird successfully recovering in the Cook Islands

Dispersal of fig seeds in the Cook Islands: introduced frugivores are no substitutes for natives

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