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 global population is estimated to number approximately 3,000,000 individuals which equates to 2,000,000 mature individuals (Partners in Flight Science Committee 2013). The European population is estimated at 54,700-186,000 pairs, which equates to 109,000-372,000 mature individuals (BirdLife International 2015). Europe forms approximately 14% of the global range, so a very preliminary estimate of the global population size is 391,000-1,330,000 mature individuals, although further validation of this estimate is needed.
This species has undergone a large and statistically significant decrease over the last 40 years in North America (71.2% decline over 40 years, equating to a 26.7% decline per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). Note, however, that these surveys cover less than 50% of the species's range in North America. In Europe, the population trend is estimated to be fluctuating (BirdLife International 2015).
Due to its nesting habits and nomadic nature, the species is vulnerable to habitat loss at any season; conversion of open habitats to agriculture, grazing, recreation, housing and resort development is a key factor in decline, as well as reforestation in some areas. Wind-turbine developments may also impact the species. In central Europe declines have been caused by drainage and the intensification of agriculture, together with persecution, rodenticide poisoning, urbanization and traffic mortality. It does not always occupy apparently suitable habitat, which may be due to levels of prey or predation or the effects of distribution and abundance. Domestic and feral cats and dogs cause disturbance (Olsen et al. 2013). Skunks have been known to prey on eggs and nestlings (Olsen et al. 2013).
Text account compilers
Ekstrom, J., Butchart, S. & Ashpole, J
BirdLife International (2019) Species factsheet: Asio flammeus. Downloaded from http://www.birdlife.org on 17/10/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 17/10/2019.