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 very 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 18,500-30,300 pairs, which equates to 36,900-60,600 mature individuals (BirdLife International 2015). Europe forms c.20% of the global range, so a very preliminary estimate of the global population size is 180,000-300,000 mature individuals, although further validation of this estimate is needed. The population is therefore placed in the band 100,000-499,999 mature individuals.
The overall population trend is suspected to be declining. The European population is estimated to be increasing (BirdLife International 2015). However the Asian population has apparently undergone a marked decline since the 1970s (Holt et al. 2013).
This species inhabits mainly rocky country with cliffs and ravines, caves, patches of woodland, scattered trees or groves, generally in undisturbed wilderness areas. It also uses open forest, taiga and other types of woodland, wooded steppe, river valleys with gorges, overgrown quarries and farmland with suitable rocky areas or cliffs. The species is monogamous and breeds from February to August in Scandinavia, however egg-laying occurs in December in France. It nests on sheltered cliff ledges or in crevices, in a cave entrance, on the ground on steep slope or on flatter ground in taiga. Occasionally it uses old tree nests of other species and rarely in hole in tree. The same site is often used for several years or in rotation with other favoured sites. Clutches are usually two to four eggs (Holt et al. 2013). It feeds mostly on mammals from small rodents to hares and birds to the size of herons and buzzards, but it also consumes reptiles, frogs, fish and larger insects. It also preys on other owl species in its range (König 2008). The species is resident in most of its range and juveniles disperse over variable distances (Holt et al. 2013).
Most declines are due to human activity. It is extremely sensitive and the slightest disturbance can cause the abandonment of the nest. Unfortunately cross-country skiing, mountaineering, alpinism and other leisure activities often take people unknowingly near nests (Tucker and Heath 1994). It suffers from human persecution and poisoning from mercury seed-dressings, and deaths through road traffic, barbed wire (Holt et al. 2013) and overhead wires (Tucker and Heath 1994) are not insignificant (Holt et al. 2013). These threats still persist despite its protected status in most countries (König 2008). A significant decline in Mediterranean countries in the 1960s is thought to be due to the effects of myxomatosis on rabbit populations (Holt et al. 2013). Egg-collectors impose a relatively high level of nest-robbing on the species (Tucker and Heath 1994).
Conservation Actions Underway
CITES Appendix II. Bern Convention Appendix II. EU Birds Directive Annex I. The species is protected in most countries within its range (König 2008). Extensive reintroduction programmes, especially in Germany, France, Belgium, Switzerland and Scandinavia aided by protection have enabled recovery in parts of Europe since the 1970s. The species is also likely to have benefited from an increased food supply created by the proliferation of refuse tips and large clearfell areas, which have increased prey species populations (Holt et al. 2013).
Conservation Actions Proposed
Nesting territories, and potential territories, should be protected from development and from extensive logging (Holt et al. 2013). Awareness should be raised of the species's susceptibility to disturbance, particularly with the public, birdwatchers and photographers (Tucker and Heath 1994). Enforcement of protection should be strengthened.
Text account compilers
Ashpole, J, Ekstrom, J., Butchart, S.
BirdLife International (2017) Species factsheet: Bubo bubo. Downloaded from http://www.birdlife.org on 18/10/2017. Recommended citation for factsheets for more than one species: BirdLife International (2017) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 18/10/2017.