LC
Montagu's Harrier Circus pygargus



Justification

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.

Population justification
The European population is estimated at 69,700-110,000 breeding females, which equates to 139,000-219,000 mature individuals (BirdLife International In prep.). Europe forms approximately 41% of the global range, so a very preliminary estimate of the global population size is 339,000-534,000 mature individuals, although further validation of this estimate is needed. It is placed in the band 300,000 to 550,000 mature individuals.

Trend justification
The global population is suspected to be decreasing owing to agricultural intensification and destruction of nests by farm machinery, over-use of pesticides and improved locust control, and loss of small mammal and bird prey species due to changing agricultural practices (Ferguson-Lees and Christie 2001). The European breeding population is thought to be decreasing by more than 10% over three generations (BirdLife International In prep.). Very little information is available on Asian breeding populations. Roost counts of overwintering birds in India during 1985-2015 found no significant decline of this species, despite overall declines in harrier numbers (Ganesh & Prashant 2018), however analysis of sightings of Montagu's Harrier in India logged on eBird suggested a moderate decline over the last 25 years (SoIB 2020).

Ecology

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).

Threats

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). 

Currently, the main threat in its breeding range is the conversion of its habitat to agricultural land, an environment in which crop gathering by combine harvesters causes frequent breeding failure in the species through nest destruction by farm machinery and increased risk of predation by native species (del Hoyo et al. 1994; Berger-Geiger et al. 2019). Intensification on this land increases this threat (Ferguson-Lees and Christie 2001), as does the increasing tendency for earlier harvest dates (Berger-Geiger et al. 2019). 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 also very highly vulnerable to the impacts of potential wind energy developments (Strix 2012; Schaub et al. 2020). Higher temperatures and aridity caused by climate change are predicted to reduce nesting success in some areas (Berger-Geiger et al. 2019). It is illegally killed in several European countries (pressures and threats data reported by EU Member States under Article 12 of the Birds Directive for the period 2013-2018). 

In its African wintering grounds, the species is under threat from 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 also reported to be used for traditional medicine in Benin (Williams et al. 2013). In India, its grassland wintering sites are under threat from grazing, burning, urbanisation and industrialisation, while intensive pesticide use may lead to reduced prey availability and direct mortality (Ganesh & Prashanth 2018).

Conservation actions

Conservation actions underway
The species is listed on CITES Appendix II, CMS Appendix II, Raptors MoU Category 2 and Bern Convention Appendix II. Strategies to protect nest sites from harvesting activities are in place throughout much of its European breeding range (Berger-Geiger et al. 2019). It is monitored by systematic breeding bird surveys in 12 European countries, representing 35% of the European countries in which it breeds (Derlink et al. 2018). It is also monitored in at least parts of its range by the International Waterbird Census (>10 records received in >50% of the years that the census has been running in the relevant region).

Conservation actions needed
There is a need for identification and protection of key wintering sites and long-term monitoring of population trends, particularly for the Asian population (Ganesh & Prashanth 2018). Threats at breeding grounds may be minimised by protection of nest sites using fenced areas and delayed harvesting where possible (Berger-Geiger et al. 2019) and preclusion of wind energy developments from core breeding areas (Schaub et al. 2020).

Acknowledgements

Text account compilers
Haskell, L.

Contributors
Ashpole, J, Khwaja, N., Harding, M., Ekstrom, J. & Butchart, S.


Recommended citation
BirdLife International (2022) Species factsheet: Circus pygargus. Downloaded from http://www.birdlife.org on 29/06/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 29/06/2022.