Justification of Red List Category
This species is declining at a moderately rapid rate, qualifying the species as Near Threatened. Declines in the core population in Spain are largely responsible for overall declines, however other local populations have also reported declines. The drivers of the decline are not entirely clear but include habitat degradation and modification.
In Europe, the breeding population is estimated to number 597,000-1,430,000 pairs, which equates to approximately 1,200,000-2,900,000 mature individuals and 1,800,000-4,300,000 individuals (BirdLife International 2021). Europe forms c.85% of the global range, so a very preliminary estimate of the global population size is 1,400,000-3,400,000 mature individuals and 2,100,000-5,100,000 individuals although further validation of this estimate is needed.
Trend data is provided from the European range. As Europe holds c. 85% of the global population, these trends are held to reflect the global population. The European population underwent a large decline during 1970-1990 (Tucker and Heath 1994), and has continued to decline. BirdLife International (2021) estimate a 7.9% decrease between 2007-2018, or 10 years; however, considering trends calculated by the Spanish Common Bird Monitoring Scheme (SACRE) and the Pan-European Common Bird Monitoring Scheme (PECBMS; EBCC 2018), it's likely that the 10 year decline falls between 20-30%. PECBMS estimates a 15% decline between 2007-2016 (10 years). Between 1980-2018, BirdLife International (2021) estimates a 38% decline in Europe, and PECBMS a 37% decline between 1996-2016. Whilst populations in Portugal and the United Kingdom are increasing, declines have been reported for both France and Italy. The population has undergone a strong increase in Portugal (A. Meirinho in litt. 2016, Regos et al. 2016) possibly owing to the availability of burnt areas (S. Herrando in litt. 2016). In the U.K. it has recently increased rapidly and extended its range northwards, reaching a total of 3,214 territories in 2006 (Wotton et al. 2009), and 1,677 territories in 2015. The last full survey, in 2006, coming after a long run of mild winters, may have recorded the population at or close to its peak (Holling et al. 2017). Keller et al. (2020) also shows an increase in breeding range across the U.K. between EBBA1 and EBBA2 (European Breeding Bird Atlas), in line with climate predicitions (Huntley et al. 2008). The population in France declined by at least 50% between 2001 and 2014 (E. Green in litt. 2016). In Italy, the population is declining although it is unclear to what extent (Monitoraggio Italiano Ornitologico and Lega Italiana Protezione Uccelli in litt. 2016). The species has abandoned previously occupied areas in Northern France, Southern Italy and Sicily (Keller et al. 2020).The population trend is unknown in Andorra (20-30 pairs). The overall population trend is therefore estimated to be decreasing at a rate of 20-29% over three generations, and is suspected to continue at the same rate between over the next ten years.
This species is restricted to southern and western Europe and north-west Africa, where it is patchily distributed but locally common to very common in Spain (including Balearic Islands), Portugal, Andorra, Morocco, Algeria, Tunisia, France (including Corsica), United Kingdom and Italy (including Sardinia) (del Hoyo et al. 2006). The European breeding population constitutes c. 85% of the global population.
It favours dense, homogeneous scrub, garrigue and low maquis c.0.5-1.5 m in height and dominated by species such as Ulex, Erica, Calluna, Rosmarinus, Genista, Cistus and Quercus coccifera (del Hoyo et al. 2006, Chiatante 2014, S. Wotton in litt. 2016). It is largely sedentary but undertakes some short-distance dispersive movements and some European birds spend the non-breeding season in north-west Africa (del Hoyo et al. 2006). It is primarily a lowland species in the north of its range but occurs to 1,800-2,000 m in the Pyrenees and north-west Africa (del Hoyo et al. 2006). The species feeds on mostly arthropods, but may also eat berries outside the breeding season (Aymí and Gargallo 2021). Breeding will occur mostly from mid-March to August (Aymí and Gargallo 2021).
In Spain, it is vulnerable to severe winters, particularly in the northern part of its range (del Hoyo et al. 2006). Cold spells in December 2001 and the winter of 2004-2005 and 2008-2009 caused high mortality in Spain (J. J. R. Encalado in litt. 2007) and France respectively (Jiguet and Williamson 2013, A. Regos in litt. 2016) , while the U.K. population was reduced to 11 pairs after the severe winter of 1962-1963 (del Hoyo et al. 2006) and again crashed in 2008 and 2010 following two cold winters (S. Wotton in litt. 2016). Research shows that the species is able to recover following population crashes brought about by freezing conditions, however this recovery is much stronger on heathland than in neighbouring early-growth forest (Jiguet and Williamson 2013). Current and future climate change are expected to alter the species's distribution in the north of its range (Huntley et al. 2008, Bradbury et al. 2011, Barbet-Massin et al. 2012). For example, the species's breeding range in the U.K. have increased in line with climate predictions (Huntley et al. 2008, Keller et al. 2020).
Increasing densities of cattle on the Spanish dehesa are causing severe habitat degradation through overgrazing (J. J. R. Encalado in litt. 2007), which may be affecting the species. Afforestation has decreased the amount of suitable habitat in parts of France and Iberia (Shirihai et al. 2001). The species is reliant on dense, low shrublands that are often created as a result of past fires. With the species peaking in abundance a short time after the initial fire (e.g. c.3-4 to 9 years post fire) when the vegetation is most suitable (Jacquet and Prodon 2009, Pons and Clavero 2010, S. Herrando in litt. 2016), changes in the pattern and frequency of wildfires as a result of fire suppression policies and climate change may reduce the area of suitable habitat for the species in Europe (Regos et al. 2015, P. Pons in litt. 2016, A. Regos in litt. 2020). Post-fire forest management can negatively affect the species through the removal of burnt trees as the species has been shown to favour a moderate coverage of logging remnants after fires (Herrando et al. 2009), however, a non-significant positive effect of salvage logging has been described for this species (Rost et al. 2013). Building log piles is known to benefit the species (Herrando et al. 2009, Rost et al. 2010). In the UK there is some evidence to show that the species is adversely affected by disturbance from people and dogs (S. Wotton in litt. 2016).
Conservation Actions Underway
Bern Convention Appendix II. EU Birds Directive Annex I. CMS Appendix II. The species was uplisted to Endangered in France in 2016 (UICN France, MNHN, LPO, SEOF and ONCFS 2016), and is listed as Endangered on the national Spanish Red List (SEO/BirdLife 2021). Population trends are monitored in parts of the species' range and it occurs in a number of protected areas. In the UK the species is reliant on ongoing heathland management and restoration (S. Wotton in litt. 2016).
Text account compilers
McGonigle, K., Fernando, E.
Ashpole, J, Butchart, S., Derhé, M., Ekstrom, J., Encalado, J.J.R., Escandell, V., Green, E., Grice, H., Herrando, S., Iñigo, A., Kirchner, F., Lega Italiana Protezione Uccelli, Mahood, S., Meirinho, A., Monitoraggio Italiano Ornitologico, Piggott, A., Pons, P., Regos, A., Rutherford, C.A., Staneva, A., Symes, A., Taylor, J. & Wotton, S.
BirdLife International (2023) Species factsheet: Curruca undata. Downloaded from http://www.birdlife.org on 01/04/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 01/04/2023.