Moustached Warbler (Acrocephalus melanopogon) has a large range, breeding across southern Europe, the Middle East and Central Asia, from Spain east to Kazakhstan. Some populations are migratory, wintering in North Africa, the Mediterranean, the Middle East, Central Asia and NW Indian Subcontinent. The population size has been roughly estimated at 434,000-712,000 mature individuals, based on an estimate of 76,100-124,000 pairs in Europe (BirdLife International 2015) and the fact that Europe is estimated to form c.35% of the global range. The population has been suspected to be stable in the absence of evidence for any declines or substantial threats (del Hoyo et al. 2006). Given the species extremely large range, stable trend and extremely large population, the species has not been considered to approach the thresholds for listing as Vulnerable against any criterion, and is consequently currently listed as Least Concern (IUCN 2017).
We have recently received information that a research project focussing on the species in five countries since 2002 has indicated that the population is declining (P. Villányi in litt. 2018). We are therefore requesting further information in order to reassess the species’s Red List status.
Our current information on the species’s conservation status will now be compared to all Red List Criteria.
Criterion A – The species’s conservation status in Europe was recently assessed for the European Red List of Birds (BirdLife International 2015). The European trend was not known, but it was believed that the species was not decreasing sufficiently rapidly to approach the thresholds under Criterion A (30% decline over ten years or three generations). The species’s global trend has previously been assumed to be stable in the absence of evidence to the contrary (del Hoyo et al. 2006). Research in five countries from 2002 has suggested a population decline (P. Villányi in litt. 2018), however we do not currently have information on the magnitude of this decline, or the proportion of the population that is experiencing this decline. Should information be available to indicate that the population is declining at a rate that would equate to a 30% or more reduction in the species’s global population across the last 13 years (three generation lengths); or in the next 13 years; or across 13 years that include both the past and the future; then the species may qualify for listing as threatened under Criterion A. If information suggests that the rate of reduction approached 30% across three generation lengths, then the species may qualify for listing as Near Threatened under Criterion A.
Criterion B – The species’s extent of occurrence (EOO) has been estimated as 11,700,000km2. The area of occupancy (AOO) has not been estimated, but is extremely unlikely to approach the threshold for Vulnerable of 2,000km2. The species therefore qualifies for listing as Least Concern under Criterion B.
Criteria C and D – The species’s population size was estimated as 434,000-712,000 mature individuals, based on an estimate of 76,100-124,000 pairs in Europe (BirdLife International 2015) and the fact that Europe is estimated to form c.35% of the global range. Although this estimate has a high level of uncertainty, even if the population is declining, the total number of mature individuals is very unlikely to approach the population thresholds for these Criteria (10,000 and 1,000 mature individuals). The species does not have a restricted AOO or number of locations such that a plausible future threat could drive the species to Critically Endangered or Extinct within a very short time. The species therefore qualifies for listing as Least Concern under Criteria C and D.
Criterion E – To the best of our knowledge no quantitative assessment of the probability of extinction has been conducted for Moustached Warbler, and so it cannot be assessed against this criterion.
To get a clearer assessment of the species’s status, information is requested on the population size, trends and threats of the Moustached Warbler since the mid-2000s, especially from outside of its European range.
In particular, to enable us to assess the magnitude of any population reduction and thus assess the species’s status under Criterion A, it will be important for us to know the rate of any detected population decline, and the locations where the decline has been estimated.
Please note that this topic is not designed to be a general discussion about the ecology of the species, rather a discussion of the species’s Red List status. Therefore, please make sure your comments are about the proposed listing.
An information booklet on the Red List Categories and Criteria can be downloaded here and the Red List Criteria Summary Sheet can be downloaded here. Detailed guidance on IUCN Red List terms and definitions and the application of the Red List Categories and Criteria can be downloaded here.
BirdLife International. 2015. European Red List of Birds. Office for Official Publications of the European Communities, Luxembourg.
del Hoyo, J.; Elliott, A.; Christie, D. 2006. Handbook of the Birds of the World, vol. 11: Old World Flycatchers to Old World Warblers. Lynx Edicions, Barcelona, Spain.
IUCN. 2017. The IUCN Red List of Threatened Species. Version 2017-3. Available at: www.iucnredlist.org (Accessed: 19 February 2018).