Justification of Red List Category
This species is listed as Endangered because it has a very small population and range, and it is now restricted to a single island where it is rare, localised and declining owing to disturbance and habitat degradation. Measures are urgently needed to regulate access to important breeding valleys and the collection of bamboo to slow its rate of decline.
The population is estimated to number a few hundred individuals by Monnet et al. (1993b). It is placed in the band 250-999 mature individuals, equating to 375-1,499 individuals in total, rounded here to 350-1,500 individuals.
The population is declining at a slow to moderate rate, owing to a number of factors, most important perhaps is the unregulated collection of bamboo.
Acrocephalus caffer is found on Tahiti in the Society Islands, French Polynesia. The species is absent from the Tahiti peninsula (Tahiti Iti) and has been rare and local throughout the 20th century, being recorded in six valleys during the period 1920-1923 (out of 14 visited) and 12 during 1986-1991 (out of 39), and estimated to number a few hundred individuals (Monnet et al. 1993b).
It occurs in bamboo thickets and second growth forests in river valleys and hillsides to 1,700 m. It feeds on insects but also takes lizards, small fish, crayfish, snails and nectar (Pratt et al. 1987, Thibault 1988). It is thought to breed exclusively in bamboo thickets (P. Raust in litt. 2007).
The development of hydro-electricity opened up the interior of the island with new roads and tracks (P. Raust in litt. 2007). This increased access has lead to a considerable increase in the exploitation of bamboo as well as invasion by the neotropical weed Miconia and an increase in tourists in four-wheel drive vehicles. These factors have modified the habitat considerably, and most worryingly have caused a loss of breeding habitat, as well as causing disturbance to birds (P. Raust in litt. 1999, P. Raust in litt. 2007). The introduction of feral cats Felis catus, rats Rattus spp. (A. Gouni in litt. 2012) and many alien bird species, including the aggressive Common Myna Acridotheres tristis, may also contribute to its rarity (Thibault 1988, Seitre and Seitre 1991).
Conservation Actions Underway
Surveys are ongoing in the Papenoo Valley (C. Blainvillain verbally 2000).
19 cm. Large, long-billed warbler with two colour-morphs. Most birds pale yellow, mottled with brownish-olive above. Dark morph all dark olive-brown. Similar spp. Tahiti Monarch Pomarea nigra blacker than dark morph, with pale blue, short bill; occur in different valleys. Voice Call a harsh churrr. Song a lively and varied series of whistles, churrs, and warbles; often long sustained. Hints Shy, skulking bird most easily located by its voice.
Text account compilers
Khwaja, N., Mahood, S., O'Brien, M., Shutes, S., Stattersfield, A., Derhé, M. & Martin, R
Gouni, A., Raust, P. & Blainvillain, C.
BirdLife International (2020) Species factsheet: Acrocephalus caffer. Downloaded from http://www.birdlife.org on 11/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 11/08/2020.