No Reed Warbler species are known to inhabit the Austral Islands today, yet their former existence in that archipelago is more than likely, given the fact that such species are found on the Cook Islands to the north and on the Tuamotu archipelago to the east.
And, there is indeed at least one record of a reed warbler that was heard singing on one of the Austral Islands – Raivavae.:
“A. v. sous-espèce ?
Raevavae: des fauvettes furent entendues par Lacan (J.-L. Mougin, comm. pers.) en mai 1968.” [1]
translation:
“A. v. subspecies?
Raevavae: warblers were heard by Lacan (J.-L. Mougin, pers. Comm.) in May 1968.“
and:
“Une espèce non identifiée d’Acrocephalus a été notée à Raivavae en 1968 mais n’a pas été retrouvé en 1990 (Seitre et Seitre 1991) et pouvait donc être un oiseau erratique.” [1]
translation:
“An unidentified species of Acrocephalus was recorded at Raivavae in 1968 but was not found in 1990 (Seitre and Seitre 1991) and could therefore be an erratic bird.“
This one, brief record may in fact refer to a last remaining tiny population of an endemic reed warbler population that went extinct so after.
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References:
[1] D. T. Holyoack; J.-C. Thibault: Contribution à l’étude des oiseaux de Polynésie orientale. Mémoire du MNHN, Série A Zoologie 27: 121-122. 1984
The Pagan Reed Warbler was endemic to Pagan, a volcanic island in the northern part of the Marianas archipelago in the Pacific Ocean.
The species reached a size of about 17 cm and superficially resembled the likewise extinct Nightingale Reed Warbler (Acrocephalus luscinius (Quoy & Gaimard)).
The Pagan Reed Warbler was restricted to the reeds around the two wetlands that exist on the island; it disappeared due to the introduction of ungulates who destroyed much of the island’s native vegetation. It was last seen in 1969 and is now clearly extinct.
This species, formerly considered a subspecies of the Nightingale Reed-Warbler (Acrocephalus luscinius (Quoy & Gaimard)) from Guam, is restricted to the tiny island of Aguiguan (also known as Aguigan or Aguijan; or Goat Island), which lies to the south of Saipan in the Mariana Islands chain. [3][4]
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The Aguiguan Reed-Warbler differs from the Nightingale Reed Warbler by its much less warm-toned upperparts, the darker flanks and belly, and the slightly shorter bill. [3]
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The island of Aguiguan is overrun with introduced goats, an eradication program conducted in 1990 was only partially successful, and the goat population on Aguijan in 1998 remained at an estimated 1500 animals. The feral goats affect the native forest by causing severe erosion and removing the understory, which is becoming dominated by the aggressively invasive Shrub Verbena (Lantana camara L.).
The reed-warbler population was estimated at only about four to 15 birds in the mid-1980s. [1]
The species was believed extinct since 1985, but was rediscovered in 1992, when two males were heard singing [2]
The Aguiguan Reed-Warbler was not seen since and is now believed to be probably finally extinct. [5]
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References:
[1] J. Engbring; F. L Ramsay; V. J. Wildman: Micronesian forest bird survey, 1982: Saipan Tinian, Aguijan, and Rota. U.S. Fish and Wildlife Service Report 1986 [2] Robert J. Craig; Ravi Chandran: Wildlife species recorded during the Aguiguan Expedition: 20-25 May, 1992. In: Robert J. Craig: The Aguiguan Expedition. Proceedings of a Symposium held at Northern Marianas College 1993 [3] Peter Kennerly; David Pearson: Reed and Bush Warblers. Christopher Helm 2010 [4] Takema Saitoh; Alice Cibois; Sayaka Kobayash; Eric Pasquet; Jean-Claude Thibault: The complex systematics of the Acrocephalus of the Mariana Islands, western Pacific. Emu 112(4): 343–349. 2012 [5] Fred Amidon; Richard J. Camp; Ann P. Marshall; Thane K. Pratt: Terrestrial bird population trends on Aguiguan (Goat Island), Mariana Islands. Bird Conservation International 24(4): 505-517. 2014
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’
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
The Tahiti Reed-Warbler (Acrocephalus caffer (Sparrman)) was described in 1786 as Sitta caffra, quasi as a nuthatch coming from southern Africa. This shows how much scientists in the 18th century understood of biogeography, biology, and taxonomy …!
This species is now the sole member of its genus leftover in the Society Islands, but in former times there were at least four distinct forms inhabiting at least four of the islands in the archipelago.
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According to DNA analyses made in 2008, it is now known that the four known reed warbler forms formerly found on the Society Islands are/were not conspecific but evolved from three separate colonization events.
Thus, the Moorea Reed-Warbler, but also the Raiatea Reed-Warbler (Acrocephalus musae (J. R. Forster)), are now regarded as full species. [1]
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The Moorea Reed-Warbler was described in 1789 (as a thrush, by the way).
The species reached a size of about 19 cm and was superficially quite similar to the other Society Islands reed-warbler species but differed from them by its conspicuously pale outher tail feathers (unlike in the depiction below).
The last approved record dates from 1981, however there appears to be a recent sighting made sometimes in 1998 or 1999 including a photo that, given the color of the tail feathers, almost certainly depicts this species. It is nevertheless now regarded as most likely extinct.
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References:
[1] Alice Cibois; Jean-Claude Thibault; Eric Pasquet: Systematics of the extinct reed warblers Acrocephalus of the Society Islands of eastern Polynesia. Ibis 150: 365–376. 2008
The Fanning Reed Warbler was originally described in 1883 as a full species but was later recognized as a subspecies of the Kiribati Reed Warbler, which is endemic to the giant Kiritimati atoll in the Line Islands group of Kiribati.
The Fanning Reed Warbler appears to inhabit two atolls north of Kiritimati, namely Tabuaeran and Teranina, it was originally described from Tabuaeran which was called Fanning Island at that time.
The reed warbler is now extinct on Tabuaeran but still inhabits Teraina, where it may even be quite common.
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The taxon is just discussed here because the birds from Tabuaeran and Teraina differ from each other insomuch that the upperparts of birds in fresh plumage from Tabuaeran apparently showed broad white fringes, giving them the appearance of being dusted with flour, while birds from Teraina are not known to show such white fringes and thus more closely resemble the nominate from Kiritimati.
In my opinion the birds from Teraina may in fact prove to be subspecifically distinct from those from Tabuaeran, making the ssp. pistor being extinct and leaving the Teraina birds unnamed. But this has apparently not yet been tested.
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References:
[1] David Pearson; Peter Kennerly: Reed and Bush Warblers. Christopher Helm 2009
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Depiction from: ‘H. B. Tristram: On the Position of the Acrocephaline Genus Tatare, with the Descriptions of two new species of the Genus Acrocephalus. The Ibis 5(1): 38-46. 1883’
A single bone, found on the Majuro atoll in the Marshall Islands, is the only evidence for the former existence of this species. [1]
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Interestingly is the fact that old oral traditions of the islanders of at least three atolls (Jaluit, Majuro, Wotho) mention a small songbird which is said to once have been common on the northern islands in the Marshall archipelago. This bird was said to live near the beaches among coral rocks on or near the floor.
The native name of this bird is, depending to the island, given as Anang, Annan or Annang. [2]
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References:
[1] David W. Steadman: Extinction and Biogeography of Tropical Pacific Birds. University Of Chicago Press 2006 [2] Dirk H. R. Spennemann: Extinctions and extirpations in Marshall Islands avifauna since European contact-a review of historic evidence. Micronesica 38(2): 253–266. 2006
The Nightingale Reed Warbler was an endemic species of Guam, where it was called Ga’kaliso, or Ga’karriso in Chamorro, the language of the native inhabitants. The species reached a size of about 17 cm.
The Nightingale Reed Warbler inhabited dense reed thickets in freshwater- and brackish marshlands, which, during the 20th century, were largely drained. Hence the reasons for the extinction of this species lie mainly in the extensive destruction of its habitat. The unintentional introduction of the Brown Tree Snake (Boiga irregularis (Merrem)), which has led to the extinction of nearly all of Guam’s native bird species, plays a minor role here.
The last individuals were seen in the year 1969.
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The island of Alamagan in the north of the Mariana Archipelago is still harboring a smaller population of reed warblers (about 300 birds), which hitherto have been assigned without any reservation to this species (resp. formerly subspecies), which, however, in a biogeographical sense must be considered completely impossible (hereto see map). The birds from the island of Alamagan are either most closely related to the species from Alamagan’s neighbor island, Pagan, the Pagan Nightingale Reed Warbler (Acrocephalus yamashinaeTakatsukasa), or even represent a distinct species.
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The reed warbler populations of all other islands in the Mariana island chain were until recently treated as subspecies of this species, but are now considered as distinct species.
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References:
[1] H. Douglas Pratt, Phillip L. Bruner, Delwyn G. Berrett: A Field Guide to the Birds of Hawaii and the Tropical Pacific. Princeton University Press 1987 [2] James D. Reichel; Gary J. Wiles; Phil O. Glass: Island extinctions: the case of the endangered Nightingale Reed-Warbler. Wilson Bull. 104(1): 44-54. 1992 [3] David Pearson; Peter Kennerly: Reed and Bush Warblers. Christopher Helm 2009 [4] Alice Cibois; Jon S. Beadell; Gary R. Graves; Eric Pasquet; Beth Slikas; Sarah A. Sonsthagen; Jean-Claude Thibault; Robert C. Fleischer: Charting the course of reed-warblers across the Pacific islands. Journal of Biogeography 38(10): 1963-1975. 2011
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reed warbler species of the Marianas known from specimens
The reed-warblers of the Society Islands were considered as subspecies of the Tahiti Reed-Warbler (Acrocephalus caffer (Sparrman)) until recently, when these forms were examined for their DNA. According to DNA analyses it is now known that the four known forms evolved from three separate colonization events. The reed-warblers of the both islands Huahine and Ra’iatea can be referred to a common ancestor and so can be conflated as two subspecies of a single species. [2]
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The Huahine Reed-Warbler was described in 1978 based on two specimens that had been collected sometimes between 1870 and 1887, the species was probably already long extinct at the date of its description.
Only about a handful of stuffed specimens exist today in several European museums.
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References:
[1] Erwin Stresemann: Birds collected during Capt. James Cook’s last expedition (1776-1780). Auk 67(1): 66-88. 1950 [2] Alice Cibois; Jean-Claude Thibault; Eric Pasquet: Systematics of the extinct reed warblers Acrocephalus of the Society Islands of eastern Polynesia. Ibis 150: 365–376. 2008
