Nesospiza sp. ‘Tristan da Cunha’

Tristan da Cunha Finch (Nesospiza sp.)

The Tristan da Cunha archipelago, which lies nearly exactly in the middle of the vast Atlantic Ocean, harbors one of the most interesting radiations known in the bird world – the Atlantic Island Finches (Nesospiza spp.).

These are at least three species, the Inaccessible Island Finch (Nesospiza acunhae Cabanis), the Nightingale Island Finch (Nesospiza questi Lowe), and Wilkin’s Finch (Nesospiza wilkinsi Lowe), which inhabit Inaccessible Island as well as Nightingale island but are absent from the island of Tristan da Cunha itself.

This, however, wasn’t always the case, since these birds were actually originally found on –  and described from that island, this population, however, disappeared sometimes around 1873, of course due to the usual reasons – habitat destruction, hunting and predation by introduced mammals. [1]

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The birds from Tristan da Cunha were not described as a distinct subspecies or whatsoever but are considered to be conspecific with the nominate form that is otherwise restricted to Inaccessible Island (see photo below). They may, however, indeed constitute a distinct form, endemic to this one island; this form is now known only from a single specimen that was collected on the island in 1817, when the species was said to be plentiful. [2]

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References:

[1] M. W. Fraser; D. J. Briggs: New information on the Nesospiza buntings at Inaccessible Island, Tristan da Cunha, and notes on their conservation. Bulletin of the British Ornithologists’ Club 112(3): 191-205. 1992 
[2] Peter G. Ryan: Taxonomic and conservation implications of ecological speciation in Nesospiza buntings on Tristan da Cunha. Bird Conservation International 18: 20-29. 2008

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Inaccessible Island Finch (Nesospiza acunhae ssp. acunhae); nominate form

Photo: Brian Gratwicke

(under creative commons license (2.0))
https://creativecommons.org/licenses/by/2.0/

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edited: 30.05.2021