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). The population trend appears to be fluctuating, and hence the species does not 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 506,000-968,000 pairs, which equates to 1,010,000-1,940,000 mature individuals (BirdLife International 2015). Europe forms c.25% of the global range, so a very preliminary estimate of the global population size is 4,040,000-7,760,000 mature individuals, although further validation of this estimate is needed.
Marked annual fluctuations have been noted within this species's European breeding range (del Hoyo et al. 2006). In Europe, trends since 1982 are uncertain (EBCC 2015).
This is a forest species but can occur in open woodland with a variety of structured vegetation: woodland margins, dense thorny bushes, clearings with rich undergrowth, isolated tree stands, young plantations, riverine thickets, hedgerows at railsides and roadsides, pastures, meadows, parks and orchards. Breeding occurs from May to July. The nest is an open elaborate cup-shaped structure coated externally with spider webs and the silk of caterpillar cocoons. It is usually hidden in dense thorny bush such as Rubus, rose (Rosa) or hawthorn (Crataegus), occasionally in juniper (Juniperus), c. 30–200 cm above ground. Clutches are three to six eggs. The diet is mainly made up of insects during the breeding season but fruits become steadily more important once breeding has finished and just before and during migration. The species is migratory, wintering in east Africa (Aymí et al. 2015).
In eastern Germany, the intensification of agriculture, ploughing of grassland and disappearance of large areas of low-intensity pastures and unproductive grassland have driven habitat loss. Population and range fluctuations may have climatic causes, as the species does not tolerate damp, cool, early-summer weather. The disappearance of Lanius collurio may have also caused declines through the interdependence of both species (Hagemeijer and Blair 1997).
Conservation Actions Underway
CMS Appendix II. Bern Convention Appendix II. EU Birds Directive Annex I. There are currently no known conservation measures for this species within Europe.
Conservation Actions Proposed
Habitat management for this species should include extensive grazing as this keeps vegetation varied and well structured and thus suitable for this species (Aymí et al. 2015).
Text account compilers
Ashpole, J, Butchart, S., Ekstrom, J.
BirdLife International (2022) Species factsheet: Curruca nisoria. Downloaded from http://www.birdlife.org on 22/05/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/05/2022.