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 stable, 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 535,000-939,000 pairs, which equates to 1,070,000-1,880,000 mature individuals (BirdLife International 2015). Europe forms c. 80% of the global range, so a very preliminary estimate of the global population size is 1,400,000-2,400,000 mature individuals, although further validation of this estimate is needed. The population is therefore placed in the band 1,000,000-2,999,999 mature individuals.
The population is suspected to be stable in the absence of evidence for any declines or substantial threats. The European population trend is unknown (BirdLife International 2015).
The primary habitat of this species is broad-leaved forest, however it adapts well to man-made and altered habitats. It is found in urban areas, clear-felled areas and intensive agricultures. In woodland habitats it inhabits mixed conifer and broad-leaved forests, sub-alpine conifer forest and conifer plantations (Hagemeijer and Blair 1997). It is monogamous and pairs for life, although is occasionally bigamous. The breeding season is from February to July (Holt et al. 1999). It nests in holes in trees, cliffs, buildings and steep river banks. Also often uses, nestboxes, the old nests of large birds, burrows of large mammals (König 2008), dreys of squirrels (Sciurus) (Holt et al. 1999) and shallow depressions on the ground at the base of a tree or beneath a bush. Typically it lays three to five eggs (König 2008). It feeds on small mammals and small birds and will also consume amphibians, reptiles, earthworms, snails, beetles and other insects and occasionally fish (Holt et al. 1999). The species is sedentary and highly territorial (Hagemeijer and Blair 1997).
In Britain, human persecution drove declines during the 19th century (Holt et al. 1999). The species is reliant on prey availability, which is often determined by woodland structure. In the north, competition with the Ural Owl (Strix uralensis) may limit the expansion of its range (Hagemeijer and Blair 1997). Locally, pesticide use, traffic and electrocution from powerlines also threaten this species (König 2008).
Conservation Actions Underway
CITES Appendix II. Bern Convention Appendix II. There are currently no known, specific conservation measures for this species.
Conservation Actions Proposed
Further research on aspects of this species’s biology is recommended (König 2008).
Text account compilers
Butchart, S., Ekstrom, J., Symes, A., Taylor, J. & Ashpole, J
BirdLife International (2019) Species factsheet: Strix aluco. Downloaded from http://www.birdlife.org on 06/12/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 06/12/2019.