Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
In Europe, the breeding population is estimated to number 2,600,000-4,680,000 pairs, which equates to 5,190,000-9,360,000 mature individuals (BirdLife International 2015).
The population is suspected to be in decline owing to ongoing habitat destruction (del Hoyo et al. 2006), although in Europe, trends between 1982 and 2013 have been stable (EBCC 2015).
This species breeds mainly in beds of reed (Phragmites), locally in stands of reedmace (Typha), growing in fresh or brackish water and rarely, in willow bushes (Salix). It shows a preference for tall reeds with thick stems, especially next to open water. In western and central Europe, egg-laying occurs from mid-May to July but begins earlier in southern Europe from early May. It lays three to six eggs in a nest, which is a deep, cylindrical cup of coarsely woven grass, reed and other plants stems and leaves, some plant down, spider webs and reed flowers and lined with finer plant material, sometimes also hair and feathers. It is built 10–200 cm above water and attached to several reed stems. The diet is mainly insects but also includes spiders (Araneae), some snails and small vertebrates. Outside the breeding season it also rarely takes fruit and berries. The species is migratory, wintering in sub-Saharan Africa (Dyrcz 2006).
The reasons of declines in Europe are not clear but may be due to climate change and habitat loss. Drainage and irrigation, decreasing reed quality, lower arthropod densities (Dyrcz 2006), land reclamation, eutrophication and reedbed die-back may be causes (Hagemeijer and Blair 1997).
Conservation Actions Underway
CMS Appendix II. Bern Convention Appendix II. There are currently no known conservation measures for this species within Europe.
Conservation Actions Proposed
Habitat may be managed for the species through the restoration of natural water level fluctuations, restoration of early successional wetland stages and the reduction of water nutrient loads (Graveland 1998).
Text account compilers
Ashpole, J, Butchart, S., Ekstrom, J. & Taylor, J.
BirdLife International (2017) Species factsheet: Acrocephalus arundinaceus. Downloaded from http://www.birdlife.org on 17/12/2017. Recommended citation for factsheets for more than one species: BirdLife International (2017) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/12/2017.