BirdLife Species Factsheet for Rodrigues Warbler BirdLife Species Factsheet for Rodrigues Fody The known population of Rodrigues Warbler Acrocephalus rodericanus declined to as few as 8 pairs and one singleton in 1979, but a slow increase followed in the 1980s and 1990s, with at least 150 birds estimated in 1999. The population was believed to have remained relatively stable until at least 2004 but more recent surveys suggest an extremely rapid recent increase in both range (area occupied increasing from 269 ha to 2,140 ha) and population density, with estimates of over 3,000 individuals (3,100-3,900) by 2010 and close to 4,000 by 2012 (Steward 2010, V. Tatayah in litt. 2011, 2012). The species is currently classified as Endangered under criterion D as its population was estimated to number fewer than 250 mature individuals, however the recent population estimates suggest that the species is likely to have considerably exceeded this threshold for at least five years and therefore warrants downlisting. If it is also estimated to have numbered >1,000 mature individuals since at least 2008, it furthermore fails to qualify as Vulnerable under criterion D1. However, it is currently also listed as Vulnerable under criterion D2 – having a very small range and subject to plausible future threats which could cause it to become Critically Endangered or Extinct within a short space of time. Rodrigues Fody Foudia flavicans is currently listed as Vulnerable under criteria D1 and D2 (a population of fewer than 1,000 mature individuals, and having a very small range within which plausible future threats could cause it to become Critically Endangered or Extinct within a short space of time). Its population has apparently also increased extremely rapidly, with an estimated population of over 8,000 individuals by 2010 (V. Tatayah in litt. 2011, 2012). If such figures can be confirmed, it is very likely that the population has numbered over 1,000 mature individuals for at least five years, and therefore no longer qualifies as Vulnerable under criterion D1. The key question for both species therefore becomes whether sufficiently severe plausible threat(s) remain such that either or both should be classified as Vulnerable under criterion D2, or whether classification as Near Threatened is more appropriate. Cyclones remain a natural threat, but following an increase in the extent of suitable habitat and expansion in both their ranges and populations, both species may now be able recover much more readily (V. Tatayah in litt. 2011). It may therefore be appropriate to reclassify both species as Near Threatened (nearly meeting criterion D2) – both remain restricted to a tiny range and there are plausible future threats which could cause population declines, but none which are likely to cause either to become Critically Endangered or Extinct within a short space of time. Comments on the revised population estimates, and the potential severity of future threats to both species are welcomed. Reference: Steward, P. (2010) Rodrigues Warbler Acrocephalus rodericanus census: Onwards and Upwards. University of East Anglia.
Contact the BirdLife Red List Team under redlistteam [at] birdlife [dot] org.
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