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The Príncipe Thrush Turdus xanthorhynchus: a newly split, ‘Critically Endangered’, forest flagship species

  • MARTIN DALLIMER (a1), MARTIM MELO (a2), NIGEL J. COLLAR (a3) and PETER J. JONES (a4)
Summary
Summary

Recently recognised as specifically distinct, the Príncipe Thrush Turdus xanthorhynchus is endemic to the island of Príncipe in the Gulf of Guinea, West Africa. Formerly treated as conspecific with the more abundant T. olivaceofuscus from the nearby island of São Tomé, the Príncipe Thrush is considered rare and likely to be restricted to primary rainforest. A 2007 survey of Príncipe comprising 177 point transect locations covering 13 sites under different land uses (six in primary forest, three in secondary forest and four in plantations) encountered 18 individuals. Thrushes were found only in primary rainforest, where overall densities were 0.10 birds ha−1, equating to a population size of 435 individuals (95% confidence intervals: 208–913). We adjusted this estimate to take into account the fact that the highest density (0.22 birds ha−1) only occurred above 600 m, giving a final estimated population size of only 364 birds (95% confidence intervals: 186–887). In light of evidence of recent declines, possibly driven by hunting pressure, in the number of mature individuals and the limited area of occurrence of the species, the IUCN Red List category for the Príncipe Thrush should be ‘Critically Endangered’ under both criteria B1a+b(iii and v) and C2a(ii). The recent designation of the primary forests of southern Príncipe as a protected area (Parque Natural d’Obô do Príncipe) provides an opportunity for the conservation of this newly described species, which we recommend is used as a flagship for the forests as a whole.

Resumo

O Tordo do Príncipe Turdus xanthorhynchus é uma espécie endémica da ilha do Príncipe no Golfo da Guiné. É uma espécie rara e restrita à floresta primária. Até estudos recentes, esta espécie era considerada uma sub-espécie do muito mais abundante T. olivaceofuscus, presente na vizinha ilha de São Tomé. Em 2007 foi feito um levantamento do Tordo do Príncipe utilizando 177 pontos de contagem dispostos em transectos cobrindo 13 áreas com diferentes utilizações do solo (seis em floresta primária, três em floresta secundária e quatro em plantações). Foram encontrados 18 indivíduos, todos em floresta primária onde as densidades médias foram de 0.10 aves por hectare, o que se traduz numa estimativa do efectivo populacional de 435 indivíduos (intervalos de confiança de 95%: 208–913). Ajustando esta estimativa para ter em conta que as densidades mais elevadas (0.22 aves por hectare) apenas ocorreram a altitudes superiores a 600 m, obtêm-se uma estimativa final de apenas 364 indivíduos (intervalos de confiança de 95%: 138–887). Tendo em consideração os declínios recentes documentados para a população do Tordo do Príncipe, aparentemente como resultado da pressão da caça, e a reduzida área de ocorrência desta espécie, a categoria da Lista Vermelha da IUCN para esta espécie é de ‘Criticamente em Perigo’ tanto segundo os critérios B1a+b(ii e v) e C2a(ii). Esta é a categoria de perigo de extinção mais alta. A recente proclamação das florestas primárias do sul do Príncipe como ‘Parque Natural d’Obô do Príncipe’ oferece uma oportunidade para a conservação desta espécie recentemente descrita e que sugerimos que seja utilizada como o estandarte para os esforços de conservação destas florestas únicas.

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Corresponding author
* Author for correspondence; e-mail: m.dallimer@sheffield.ac.uk
References
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Bird Conservation International
  • ISSN: 0959-2709
  • EISSN: 1474-0001
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