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.
The European population is estimated at 54,500-92,200 breeding females, which equates to 109,000-184,000 mature individuals (BirdLife International 2015). Europe forms approximately 41% of the global range, so a very preliminary estimate of the global population size is 266,000-449,000 mature individuals, although further validation of this estimate is needed. It is placed in the band 100,000 to 499,999 mature individuals.
The population is thought to be decreasing owing to over-use of pesticides and improved locust control, agricultural intensification and destruction of nests by farm machinery and loss of small mammal and bird prey species due to changing agricultural practices (Ferguson-Lees and Christie 2001). In Europe the population size trend is unknown (BirdLife International 2015). In the EU27 the population size is estimated to be decreasing by less than 25% in 23.7 years (three generations).
Behaviour This is a migratory species, wintering in sub-Saharan Africa and southern Asia (del Hoyo et al. 1994, Ferguson-Lees and Christie 2001). It leaves its breeding grounds in August and September, beginning their return in March and April (del Hoyo et al. 1994, Snow and Perrins 1998). Birds tend to migrate on broad fronts, but there are concentrations in Gibraltar and along the Rift Valley (del Hoyo et al. 1994, Ferguson-Lees and Christie 2001). Nevertheless it will readily migrate over expanses of water (Brown et al. 1982). Birds tend to hunt alone, although do gather at high prey concentrations and will roost in groups of often over 50, sometimes communally with C. macrourus and C. aeruginosus (Ferguson-Lees and Christie 2001). Habitat It is a bird of open country, usually in lowlands but occurring up to 1,500 m in central Asia, and on its African wintering grounds up to 4,000 m (del Hoyo et al. 1994). Diet Small birds and mammals form the majority of its diet; voles are a particularly dominant food source locally in abundant areas (del Hoyo et al. 1994). Breeding site It nests in tall vegetation on the ground (del Hoyo et al. 1994). Management information Tall vegetation must be left during the breeding season, with high rates of chick mortality when this is harvested on agricultural land; key management practices include moving nestlings to safe places during harvesting, and leaving areas unharvested around the vicinity of nests (del Hoyo et al. 1994).
In the past, the use of organochlorine pesticides seemed to cause a decline in Europe and probably to a lesser extent also in Africa (Brown et al. 1982, Ferguson-Lees and Christie 2001); further causes of declines on its wintering grounds have been locust control and droughts in the Sahel (Ferguson-Lees and Christie 2001) and habitat degradation through wood harvesting, overgrazing and burning (Thiollay 2006). It is currently in decline owing to the conversion of its habitat to agricultural land, an environment in which crop gathering by combine harvesters causes frequent breeding failure in the species (del Hoyo et al. 1994). Intensification on this land increases this threat (Ferguson-Lees and Christie 2001). It is commensal with some forms of agriculture, and changes in these practices could leave it potentially vulnerable by depleting its supply of small birds and mammals to prey on (del Hoyo et al. 1994, Ferguson-Lees and Christie 2001). It is very highly vulnerable to the impacts of potential wind energy developments (Strix 2012).
Text account compilers
Butchart, S., Ekstrom, J., Harding, M., Khwaja, N. & Ashpole, J
BirdLife International (2018) Species factsheet: Circus pygargus. Downloaded from http://www.birdlife.org on 19/08/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/08/2018.