A myna problem: alien species no obstacle to recovery for the Mangaia kingfisher

Tom Thacker,Yolanda Van Heezik,Philip J Seddon,Gerald Mccormack

doi:10.1017/s0030605320000071

Tom Thacker, Yolanda Van Heezik + Show 2 more

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https://doi.org/10.1017/s0030605320000071

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Abstract

AbstractEndemic island species are of conservation interest as unique taxa, often with restricted populations, but many are data poor. The Mangaia kingfisherTodiramphus ruficollaris, known locally as the tanga‘eo, is endemic to the island of Mangaia in the Cook Islands, and categorized as Vulnerable on the IUCN Red List. The population size has not been estimated since 1996, despite concerns over habitat loss and competition with an invasive species, the common mynaAcridotheres tristis. We provide new population estimates for both the tanga‘eo and the common myna, using the same methodology as previous estimates. During December 2018–February 2019 we surveyed with distance sampling along 73 line transects walked across the six habitat types on Mangaia. We estimate there are 4,106 tanga‘eo on Mangaia (95% CI 3,191–5,283), a dramatic 7–8 fold increase compared to the previous estimate of 393–764. We estimate there are 13,350 common myna (95% CI 10,998–16,206), a slight increase, although densities in the two most favoured habitats for myna have declined. There is no evidence that the common myna poses a threat to the viability of the tanga‘eo population, as the latter has increased despite a much larger population of common myna. Presumed declines in the tanga‘eo population in the past were probably a result of habitat loss as a result of the cultivation of pineapplesAnanas comosusfor export, an industry that collapsed in the 1980s. We recommend a review of the IUCN Red List status of the tanga‘eo.

Highlights

In the face of unprecedented losses in global biodiversity, conservation efforts have increasingly targeted endemic species in biodiversity hotspots (Brooks et al, )
Tanga‘eo were not detected in the coastal scrubland, but were otherwise recorded in each of the other five habitats; common myna were detected in all six habitat types
The pooled coefficient of variation (CV) for all habitat types was . %; secondary forest had the smallest CV ( . %) and coastal. This is only the second population estimate for the tanga‘eo on Mangaia using distance sampling, and it indicates that the population has increased since

Summary

Introduction

In the face of unprecedented losses in global biodiversity, conservation efforts have increasingly targeted endemic species in biodiversity hotspots (Brooks et al, ). The. GERALD MCCORMACK Cook Islands Natural Heritage Trust, Rarotonga, Cook Islands. Islands of Polynesia and Micronesia comprise one such hotspot (Myers et al, ). For many species, a lack of available data has impeded attempts to devise conservation management plans (Bland et al, ). The Mangaia kingfisher Todiramphus ruficollaris, known locally as the tanga‘eo, is endemic to the island of Mangaia in the Cook Islands in the tropical South Pacific, and is categorized as Vulnerable on the IUCN Red List (BirdLife International, )

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