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 but is suspected to be stable in the long term, 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 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.
Partners in Flight Science Committee (2020) estimate the North American population to number c.130,000 individuals (c.87,000 mature individuals) and the global population to number c.250,000 individuals (c.167,000 mature individuals). The European population is estimated at 10,400-46,200 pairs, which equates to 20,800-92,400 mature individuals (BirdLife International in prep.). Europe forms approximately 13% of the global range, so a very preliminary estimate of the global population size is 160,000-711,000 mature individuals, although further validation of this estimate is needed. The population is precautionarily placed in the band 100,000-499,999 mature individuals however the actual population could be larger.
The overall trend is likely to be fluctuating according to small-mammal prey availability. The population trend in North America is unclear, with Christmas Bird Count data showing a variable trend with irruptive years (Partners in Flight 2021). Note that these surveys cover less than 50% of the species's range in North America. In Europe the population in stable (BirdLife International in prep.).
The species is dependent on rodent populations and numbers fluctuate with the abundance of small rodents. Shooting and trapping occur in some areas (Duncan & Duncan 2020), and the species is sometimes used for falconry in Scandinavia (Duncan 1993, cited in Duncan & Duncan 2020). Vehicle or train collisions have also been recorded as causes of death in Ontario (K. McKeever, cited in Duncan & Duncan 2020). Clear cutting of forests and plantation development are likely to have reduced nest-site and hunting-perch availability in North America, although this may also have increased prey abundance (Duncan & Duncan 2020). Fire suppression has also resulted in habitat degradation (N. Barichello, cited in Duncan & Duncan 2020). The species is known to be vulnerable to West Nile Virus (Komar 2003). There is no data on the effect of pesticides on the species, however other owl species are known to be killed by consuming poisoned small mammals (Duncan & Duncan 2020). Climate change is predicted to cause dramatic declines in the species's range as forests shrink (Virkkala et al. 2008), and may also cause a collapse in vole population cycles (Cornulier et al. 2013).
Conservation actions underway
CITES Appendix II, Raptors MOU Category 3, EU Birds Directive Annex I.
Conservation actions needed
Modify clear-cut logging practices to create more profitable hunting habitats - optimal conditions result from a mix of old forest and variably sized clear-cuts <100ha (Duncan & Harris 1997; Duncan & Duncan 2020). Nest boxes may be useful for mitigating local loss of nest sites (Duncan & Duncan 2020).
Text account compilers
Ashpole, J, Butchart, S. & Ekstrom, J.
BirdLife International (2022) Species factsheet: Surnia ulula. Downloaded from http://www.birdlife.org on 03/07/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 03/07/2022.