Acrocephalus astrolabii Holyoak & Thibault

Mangareva Reed Warbler (Acrocephalus astrolabii)

The Mangareva Reed Warbler is one of the most enigmatic birds that we know of, despite being known from two specimens; their origin was unknown for a very long time but they are now strongly believed to have indeed been collected on the Gambier Islands. [4]

The species reached a size of about 17 cm; it was uniformly warm brown colored, slightly darker dorsally, it had rather robust, stout legs and a very long, straight beak. 

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The Mangareva Reed Warbler is mentioned briefly in a little description of Mangareva’s native bird life that was made in the middle of the 19th century.:

Of the feathered tribe, oceanic bird form the greater part; but even these are rare compared with the numbers that usually frequent the islands of the Pacific, arising, no doubt, from the Gambier Islands being inhabited. The whole consist of three kinds of tern, the white, black, and slate-coloured – of which the first are most numerous, and the last very scarce; together with a species of procellaria, the white heron, and the tropic and egg birds. Those frequent the shore are a kind of pharmatopus, curlew, charadrine, and totanus; and the woods, the wood-pigeon, and a species of turdus, somewhat resembling a thrush in plumage, but smaller, possessing a similar though less harmonious note.” [1]

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The Mangareva Reed Warbler may have disappeared sometimes after but was still known by the inhabitants of the Gambier Islands.: 

She [the daughter of the Chief of the island of Taravai] has not seen the “Komaku” herself, but her father, the Chief, has. He gave us the name and says he saw them about thirty or forty years ago.” [2]

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Depiction from: ‘Whitney South Sea Expedition of the American Museum of Natural History: Voyage of the ‘France’ from Timoe Atoll to the Mangareva Islands; Voyage to Marutea. April 25 – May 14, 1922. Extracts from the Journal of Ernest H. Quayle; Assistant Field Naturalist. Book XXV through Book XXVIII. April 1 – June 24, 1922’ 

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It is possible that the Mangareva Reed Warbler somehow managed to survive to the middle 19th century at least on the tiny motus (coral islets) that build the fringe reef surrounding the island of Mangareva.:

Signalons aussi qu’une fauvette fut observée sur l’îlot Tepapuri en 1971 (Thibault, 1973b). Ce dernier oiseau, blanchâtre dessus et brun dessous, devait être un erratique de la forme habitant, les atolls au nord des Gambier, A. caffer ravus.“ [3]  

translation:  

Note also that a warbler was observed on Tepapuri islet in 1971 (Thibault, 1973b). This last bird, whitish above and brown below [I’m quite sure that it should be exactly reversed], must have been an erratic of the form inhabiting the atolls north of the Gambier, A. caffer ravus.” 

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References:

[1] Narrative of a voyage to the Pacific and Beering’s Strait, to co-operate with the polar expeditions : performed in His Majesty’s ship Blossom, under the command of Captain F. W. Beechey in the years 1825, 26, 27, 28. London: Henry Colburn and Richard Bentley 1831
[2] Whitney South Sea Expedition of the American Museum of Natural History: Voyage of the ‘France’ from Timoe Atoll to the Mangareva Islands; Voyage to Marutea. April 25 – May 14, 1922. Extracts from the Journal of Ernest H. Quayle; Assistant Field Naturalist. Book XXV through Book XXVIII. April 1 – June 24. 1922 
[3] D. T. Holyoak; J.-C. Thibault: Contribution à l’étude des oiseaux de Polynésie orientale. Mémoires du Muséum national d’histoire naturelle 127(1): 1-209. 1984 
[4] Alice Cibois; Jean-Claude Thibault; Eric Pasquet: Molecular and morphological analysis of Pacific reed warbler specimens of dubious origin, including Acrocephalus luscinius astrolabii. Bulletin on the British Ornitologists’ Club 131(1): 32-40. 2011

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edited: 12.01.2024