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.
The breeding population in Europe is estimated at 20,000,000-37,000,000 pairs, which equates to 40,100,000-74,100,000 mature individuals (BirdLife International 2015). Europe forms approximately 45% of the global range, so a very preliminary estimate of the global population size is 98,000,000-165,000,000 mature individuals, although further validation of this estimate is needed.
In Europe, trends between 1980 and 2013 show that populations have undergone a moderate decline (EBCC 2015).
This species is found in boreal forests dominated by Norway spruce (Picea abies) and fir (Abies). On Atlantic islands it uses laurel (Laurus) forest or pine (Pinus) stands with well-developed undergrowth of tree-heath (Erica), but also conifer stands of indigenous short-leaved juniper (Juniperus brevifolia) or introduced Japanese cedar (Cryptomeria japonica). Outside the breeding season, and especially during migration, it will use mixed and deciduous forests, shrub vegetation and gardens and parks. Nesting begins at the end of March and both sexes build the nest (Martens and Päckert 2015), which is an almost spherical cup of moss, lichens, cobwebs, feathers, and hair, in three distinct layers and with a small entrance at the top. Clutches are typically nine to eleven eggs (Snow and Perrins 1998). It feeds mainly on arthropods and is generally adapted to small-sized prey. The species is mostly migratory (Martens and Päckert 2015).
Severe winter conditions, particularly if they persist for lengthy periods over wide areas of the non-breeding range, can significantly reduce population levels, however it is capable of rapid recovery (Martens and Päckert 2015).
Conservation Actions Underway
Bern Convention Appendix II. There are currently no known conservation measures for this species within Europe.
Conservation Actions Proposed
As this species is thought to be declining in Europe (Birdlife International 2015), research may be needed to determine it causes and potential conservation measures.
Text account compilers
Ekstrom, J., Butchart, S. & Ashpole, J
BirdLife International (2019) Species factsheet: Regulus regulus. Downloaded from http://www.birdlife.org on 24/08/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/08/2019.