email a friend
printable version
NT
Rodrigues Warbler Acrocephalus rodericanus

Justification
This species has been downlisted from Endangered following evidence that its population is increasing and is now much larger than previously estimated. It is listed as Near Threatened on the basis that it occupies a tiny range and remains susceptible to stochastic events and the impacts of introduced species, such that it could qualify as threatened within one or two generations.

Taxonomic source(s)
Dowsett, R. J.; Forbes-Watson, A. D. 1993. Checklist of birds of the Afrotropical and Malagasy regions. Tauraco Press, Li
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.

Synonym(s)
Bebrornis rodericanus Sibley and Monroe (1990, 1993)

Identification
13.5 cm. Medium-sized, drab warbler. Uniformly olive-brown upperparts with paler, yellowish-buff underparts. Long bill with pink lower mandible. Erect crown feathers impart crested appearance. Voice Harsh, chattering alarm call, soft, melodic song. Hints Tail habitually jerked up and down.

Distribution and population
Acrocephalus rodericanus, having once been very common on Rodrigues, Mauritius, declined steadily until 1979, when eight pairs and a singleton were counted (but others probably overlooked). Since 1982, there has been a steady increase in its range (C. Jones in litt. 2000). In 1999, the population was estimated to number at least 150 individuals (Showler 1999, Showler et al. 2002), and surveys up until 2004 suggested there was no change since then (A. Cristinacce and C. Jones in litt. 2005); however, the population has since risen extremely rapidly to number over 3,000 individuals (3,100-3,900) by 2010 (Steward 2010, C. Jones in litt. 2010, V. Tatayah in litt. 2011, 2012).

Population justification
In 1999, the population was estimated to be no fewer than 150 individuals, and it remained at this level until 2004 at least (A. Cristinacce and C. Jones in litt. 2005). The population has since risen rapidly to number over 3,000 (3,100-3,900) individuals by 2010 (Steward 2010, C. Jones in litt. 2010, V. Tatayah in litt. 2011) and close to 4,000 by 2012 (V. Tatayah in litt. 2012). The population is therefore estimated at 3,000-4,000 individuals, assumed to include c.2,000-2,700 mature individuals. It has been noted that the current methodology for censusing this species (Showler 2002, Steward 2010) was designed for low population densities and could now over-estimate numbers (P. Steward in litt. 2013).

Trend justification
Surveys suggest that the population was stable between 1999 and 2004 (A. Cristinacce and C. Jones in litt. 2005), but has since risen rapidly to number over 3,000 (3,100-3,900) individuals by 2010 (Steward 2010, C. Jones in litt. 2010, V. Tatayah in litt. 2011) and close to 4,000 by 2012 (V. Tatayah in litt. 2012).

Ecology
It is a territorial insectivore adapted to dense thickets in remaining, largely exotic, vegetation. The low intensity of vegetation cutting by humans appears to promote such dense growth. In 1999, a survey found 78% of the population in habitat dominated by introduced jamrosa Syzygium jambos where the highest densities (2.3 individuals/ha) are found (Showler 1999). The species is also known at lower densities (0.5/ha) in plantations of Swietenia, Tabebuia and Araucaria sp. However other factors, incompletely understood, greatly influence its distribution as demonstrated by the areas of apparently suitable habitat as yet uncolonised (Showler et al. 2002). Restored native forests were found to support the highest densities of the species (Steward 2010).


Threats
Timber harvesting, subsistence farming and feral livestock have reduced the native habitat to savanna with scattered trees. Currently, the main threat is predation and/or competition from introduced animals such as rats and feral cats (Showler et al. 2002). Sustained periods of drought (reducing invertebrate levels), cyclones, and the destruction and further degradation of remaining suitable habitat are additional problems (Showler et al. 2002). It has survived alongside the Black Rat Rattus rattus for a long time (C. Jones in litt. 2000), but nest predation by this species was believed to be a major factor suppressing its population recovery (Showler et al. 2002). In addition, the fledging success of undisturbed nests appears low, possibly due to food availability (Showler et al. 2002). Human disturbance may be an additional problem at some localities (Showler 1999).

Conservation Actions Underway
Habitat protection and reforestation, spurred by the need for watershed protection, have been key to the recovery of this species, aided by the recent absence of catastrophic cyclones. Much reforestation has involved exotic trees, although native ecosystem rehabilitation has been started at some sites, including nearby islands and the two Conservation Management Areas: Grande Montagne and Anse Quitor (both 0.1 km2). Sites are fenced to exclude grazing animals and woodcutters, exotic plants removed and native species replanted. There has been an accompanying public awareness campaign (Safford 2001). A probable decline in agriculture may have also contributed to habitat availability and the recovery of the species (P. Steward in litt. 2013).
Conservation Actions Proposed
Continue a consistent long-term monitoring programme. Initiate further research into habitat use and breeding success (Showler 1999). Assess the effects of nest predation by introduced species (Showler 1999). Continue rehabilitation of the near-shore island reserves of Ile aux Cocos and Ile aux Sables, plus Anse Quitor (WWF/IUCN 1994, Showler 1999) and Grande Montagne (V. Tatayah in litt. 2012). Investigate the potential of Ile aux Cocos, Ile aux Sables and Anse Quitor to support this species (WWF/IUCN 1994, Showler 1999) and consider translocations if appropriate.

References
Safford, R. J. 2001. Mauritius. In: Fishpool, L.D.C.; Evans, M.I. (ed.), Important Bird Areas in Africa and associated islands: Priority sites for conservation, pp. 583-596. Pisces Publications and BirdLife International (BirdLife Conservation Series No.11), Newbury and Cambridge, UK.

Showler D. A., Cote, I. M., Jones C. G. 2002. Population census and habitat use of Rodrigues Warbler Acrocephalus rodericanus . Bird Conservation International 12(3): 211-230.

Showler, D. A. 1999. Population census and habitat use of Rodrigues Warbler Acrocephalus rodericanus (Aves: Sylviidae).

Steward, P. 2010. 2010 Rodrigues Warbler Acrocephalus rodericanus census: Onwards and Upwards. University of East Anglia.

WWF/IUCN. 1994. Centres of plant diversity: a guide and strategy for their conservation. World Wide Fund for Nature and International Union for Conservation of Nature and Natural Resources, Cambridge, U.K.

Further web sources of information
Alliance for Zero Extinction (AZE) species/site profile. This species has been identified as an AZE trigger due to its IUCN Red List status and limited range.

Click here for more information about the Alliance for Zero Extinction (AZE)

Explore HBW Alive for further information on this species

View photos and videos and hear sounds of this species from the Internet Bird Collection

Text account compilers
Ekstrom, J., McClellan, R., Pilgrim, J., Shutes, S., Symes, A., Taylor, J. & Warren, B.

Contributors
Cristinacce, A., Jones, C., Tatayah, V. & Steward, P.

Recommended citation
BirdLife International (2014) Species factsheet: Acrocephalus rodericanus. Downloaded from http://www.birdlife.org on 23/10/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/10/2014.

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Rodrigues warbler (Acrocephalus rodericanus) 0

Key facts
Current IUCN Red List category Near Threatened
Family Sylviidae (Old World warblers)
Species name author (Newton, 1865)
Population size 2000-2700 mature individuals
Population trend Increasing
Distribution size (breeding/resident) 21 km2
Country endemic? Yes
Links to further information
- Additional Information on this species