Montagu's Harrier Circus pygargus Scientific name definitions

39–49 cm; male 227–305 g, female 254–445 g; wingspan 102–123 cm (1 Ferguson-Lees, J., and D. A. Christie (2001). Raptors of the World. Christopher Helm, London, UK. Close ).  Normal male has black primaries and black bands across secondaries (1 above, 2 below ) that help distinguish it from male C. macrourus; narrow white rump. Female c. 11% larger than male, slightly paler above than female C. macrourus and C. cyaneus. Non-overlapping tarsus length of pygargus (55·2–67·1) and macrourus (70·6–77·8) separate females of these species in museum collections and in the hand (2 Clark, W.S. and Clarke, R. (1998). Differences in tarsal length between adult female Montagu’s and Pallid harriers: an easy method to separate specimens. Bull. Brit. Orn. Club. 118(1): 52-54. Close ). In melanistic morph male largely blackish, female chocolate-coloured with grey base to undersides of primaries. Juvenile darker above than female, with rufous underbody and underwing coverts; unstreaked below. Irides, cere and feet of adults yellow, bill blackish-grey; irides of juveniles dark grey in male, brown in female (1 Ferguson-Lees, J., and D. A. Christie (2001). Raptors of the World. Christopher Helm, London, UK. Close ).

• Pallid x Montagu's Harrier (hybrid) Circus macrourus x pygargus

NW Africa and S & C Europe E through Ukraine, W Russia and Caspian lowlands to Kazakhstan, upper R Yenisey and extreme NW China (W Xinjiang). Winters in Africa S of Sahara and Indian Subcontinent S to Sri Lanka.

Open areas with grass or shrubs; generally flat or undulating ground, less often in steeper terrain; from totally undisturbed habitats to those heavily transformed by humans, although sometimes avoids nesting in altered habitats (3 Martínez, J.A., López, G., Falcó, F., Campo, A. and de la Vega, A. (1999). Breeding and hunting habitat of the Montagu’s Harrier Circus pygargus in La Mata-Torrevieja Natural Park (Alicante, SE of Spain): Effects of habitat structure and prey density. Ardeola. 46(2): 205-212. Close ). Grasslands, meadows, fields of cereal grains (wheat, barley, rye), fallow fields, heath, moor, scrubland, marshes and reedbeds, bogs, peatland, young conifer plantations. Preferred nesting habitat in Poland is in sedge meadows with taller, denser vegetation relative to random sites (4 Wiącek, J. (2009). Nest site selection of Montagu’s Harrier Circus pygargus breeding in natural habitats in eastern Poland. Ardea. 97(1): 117-119. Close ); in Kazakhstan, most nests are placed in brushy areas at forest-steppe ecotone (5 Terraube, J., Arroyo, B.E., Mougeot, F., Katzner, T.E. and Bragin, E.A. (2010). Breeding biology of Montagu’s Harrier Circus pygargus in north-central Kazakhstan. Journal of Ornithology. 151(3): 713-722. Close ). Mainly at low elevations, but up to 1500 m on nesting grounds in C Asia and to 4000 m on wintering grounds in Africa. Perches on small knolls, rocks or trees; roosts on ground, amidst vegetation; sometimes roosts colonially. Exceptional winter roost in NW India with at least 3000 harriers, c. 75% this species (6 Clarke, R., Prakash, V., Clark, W.S., Ramesh, N. and Scott, D. (1998). World record count of roosting harriers Circus in Blackbuck National Park, Velavadar, Gujarat, north-west India. Forktail. 14: 70-71. Close ).

Migratory, wintering in sub-Saharan Africa , Indian Subcontinent and Sri Lanka; few winter records in Europe and Middle East . In one study in Spain, adults left nesting territories in Jun and moved to higher-elevation shrublands and cultivated areas where they remained until southward migration (7 Limiñana, R., Soutullo, A., López-López, P. and Urios, V. (2008). Pre-migratory movements of adult Montagu’s Harriers Circus pygargus. Ardea. 96(1): 81-90. Close ). Leaves European breeding grounds mainly in Aug–Sept, and returns in Apr–May; migrates on broad fronts. Southbound migrants pass over Israel from 10 Aug–10 Nov, with peak passage in first half of Sept (8 Alon, D., B. Granit, J. Shamoun-Baranes, Y. Leshem, G. M. Kirwan, and H. Shirihai (2004). Soaring bird migration over northem Israel in autumn. British Birds 97(4):160–182. Close ). Of two females fitted with satellite transmitters in The Netherlands, one made it to Morocco before her transmitter failed, and the other was killed at her wintering site in N Nigeria; both left the nesting grounds in Aug (9 Trierweiler, C., Koks, B.J., Drent, R.H., Exo, K.-M., Komdeur, J., Dijkstra, C. and Bairlein, F. (2007). Satellite tracking of two Montagu’s Harriers (Circus pygargus): dual pathways during autumn migration. Journal of Ornithology. 148(4): 513-516. Close ). Birds tagged with satellite transmitters at their breeding grounds in NE Spain wintered in the W Sahel region (N Senegal, S Mauritania and S Mali); autumn migration started in late Aug–early Sept and lasted 16 days on average (range 8–25 days, n = 9); spring migration started in mid Mar, birds arriving at the breeding grounds in mid Apr (10 Limiñana, R., Soutullo, A., Urios, V. and Reig-Ferrer, A. (2012). Migration and wintering areas of adult Montagu’s Harriers (Circus pygargus) breeding in Spain. Journal of Ornithology. 153(1): 85–93. Close ).

Small ground birds, including many of their young in breeding season; small mammals, mainly voles, which when abundant can constitute nearly all of diet. Lizards and especially large insects (e.g. locusts, grasshoppers, mantids) important locally and in winter quarters (11 Arroyo, B.E., King, J.R. and Palomares, L.E. (1995). Observations on the ecology of Montagu’s and Marsh harriers wintering in north-west Senegal. Ostrich. 66(1): 37-40. Close ); e.g. birds at a large winter roost in India prey heavily on locusts (6 Clarke, R., Prakash, V., Clark, W.S., Ramesh, N. and Scott, D. (1998). World record count of roosting harriers Circus in Blackbuck National Park, Velavadar, Gujarat, north-west India. Forktail. 14: 70-71. Close ). Diet of nesting birds in Kazakhstan composed mainly of lizards (54%) and small mammals (17%) (5 Terraube, J., Arroyo, B.E., Mougeot, F., Katzner, T.E. and Bragin, E.A. (2010). Breeding biology of Montagu’s Harrier Circus pygargus in north-central Kazakhstan. Journal of Ornithology. 151(3): 713-722. Close ). Hares (Lepus granatensis) preferred prey of breeders in Spain, although nestling birds increased in diet later in nesting season (12 Arroyo, B.E. (1997). Diet of Montagu’s Harrier Circus pygargus in central Spain: analysis of temporal and geographic variation. Ibis. 139(4): 664-672. Close ); productivity was highest in years when hares were abundant and dominated diet (13 Arroyo, B.E. and García, J.T. (2006). Diet composition influences annual breeding success of Montagu’s Harriers Circus pygargus feeding on diverse prey. Bird Study. 53(1): 73-78. Close ). Avian prey mostly small passerines, especially larks, and some partridge chicks. Hunts like other harriers, with low, slow flight , quartering narrow strip of land in straight line upwind, and dropping onto prey; nearly always captures prey on ground.

Generally silent outside breeding season. Display call of male is a cackling “kek..kek..kek...”, typically given in courtship flight, with female replying with a softer, faster “kekekekek”. A similar call is given when alarmed or annoyed. Also a high-pitched squealing whistle  “keeee” or “keeee-eh” used in various contexts, such as food begging and soliciting.

Laying mostly in May–Jun; from mid April in SW Spain (14 Corbacho, C., Sánchez, J.M. and Sánchez, A. (1997). Breeding biology of Montagu’s Harrier Circus pygargus L. in agricultural environments of southwest Spain: comparison with other populations in the western Palearctic. Bird Study. 44(2): 166-175. Close ) and Morocco. Solitary, or in loose groups of up to 10s of pairs; males occasionally bigamous, and females very rarely polyandrous (15 Arroyo, B. (1996). A possibly case of polyandry in Montagu’s Harrier. Journal of Raptor Research. 30(2): 100-102. Close ). Nests on ground , in tall, dense vegetation, e.g. grassland, cereal fields, reedbeds, brushy scrub and young conifer plantations. Nest is small, narrow platform, 20–40 cm wide, made of grass stems or thin twigs. Normally 3–5 eggs (1–8), laid at interval of 1·5–3 days; average size 41·2 mm × 32·9 mm (16 Corbacho, C. and Sánchez, J.M. (2000). Clutch size and egg size in the breeding strategy of Montagu’s Harrier Circus pygargus in a Mediterranean area. Bird Study. 47(2): 245-248. Close ); replacement clutch can occur; incubation 28–29 days per egg, by female. Chicks fed by female, but prey mostly caught by male; chicks have first and second down white , variably tinged buff; fledging 30–40 days; c. 2 weeks later chicks start to hunt alone, initially catching insects. Sexual maturity normally at 2–3 years, sometimes in 1st year. Up to 4 chicks fledge; breeding success very variable and highly influenced by human interference, predation and availability of prey, particularly voles. Clutch size (mean = 4·3), productivity (2·7 fledglings/pair) and nesting success (84·4%) particularly high for pairs nesting in natural shrublands in NE Spain (17 Limiñana, R., Surroca, M., Miralles, S., Urios, V. and Jiménez, J. (2006). Population trend and breeding biology of Montagu’s Harrier Circus pygargus in a natural vegetation site in northeast Spain. Bird Study. 53(2): 126-131. Close ). Oldest recorded bird 16 years.

Not globally threatened (Least Concern). CITES II. Has declined, mainly due to loss and transformation of natural or semi-natural habitats and high rate of breeding failure in agricultural areas, in turn caused by nestlings dying following harvesting of crops (18 Castaño López, J.P. (1995). Efecto de la actividad de siega y causas de fracaso reproductive en una poblacion de Aguilucho Cenzio (Circus pygargus L.) en el se de Ciudad Real. Ardeola. 42(2): 167-172. Close , 19 Millon, A., Bourrioux, J.-L., Riols, C. and Bretagnolle, V. (2002). Comparative breeding biology of Hen Harrier and Montagu’s Harrier: an 8-year study in north-eastern France. Ibis. 144(1): 94-105. Close ); also vulnerable to contamination from PCBs and pesticides (20 Denker, E., Büthe, A., Glimm, D., Hölker, M., Prünte, W. and Trendelkamp, T. (2003). Changes in the DDT and PCB burden in life stages of Montagu’s (Circus pygargus) and Marsh Harriers (Circus aeruginosus) from North-Rhine Westfalia, Germany. Journal of Ornithology. 144(4): 411-417. Close ) and mortality from colliding with wind turbines. In some areas stable (perhaps in parts of former USSR), even with local increases. Nowadays highly dependent on cultivation and very vulnerable to changes in agricultural practices. In early 1990s, possibly c. 7000 pairs in W Europe: c. 3000 pairs in France, c. 2000 pairs in Spain , 900–1200 pairs in Portugal, c. 110 pairs in Germany, 50–60 pairs in Sweden, 25–30 pairs in Denmark; also c. 150 pairs in Hungary, perhaps 30–50 pairs in Bulgaria, c. 200 pairs in Estonia, 50–150 pairs in Latvia, 30 pairs in Lithuania, and 480–530 pairs in Poland; estimated 600–1100 pairs in Byelorussia (Belarus), and 25,000 pairs in European Russia; formerly very common in Ukraine, but in decline since 1930s, and now remains comparatively common only in NE and E. Additional small populations in other European countries; 10s of pairs in Morocco; perhaps 50–100 pairs in Turkey; very little information available on Asian populations.

More recently, BirdLife International estimated 35,000–65,000 pairs in Europe in 2004, representing 50–74% of global population; highest numbers in Russia (20,000–35,000 pairs), Spain (2500–10,000), France (3800–5100) and Belarus (3000–5000). At Castellon province, Spain, numbers of pairs nesting in natural shrublands increased from 3 in 1981 to 98 in 2003; high productivity and population increase perhaps due to lower nest predation in natural vegetation (17 Limiñana, R., Surroca, M., Miralles, S., Urios, V. and Jiménez, J. (2006). Population trend and breeding biology of Montagu’s Harrier Circus pygargus in a natural vegetation site in northeast Spain. Bird Study. 53(2): 126-131. Close ). Also in Spain, breeders selected natural salt marsh and reedbed habitats and avoided human-altered habitats (3 Martínez, J.A., López, G., Falcó, F., Campo, A. and de la Vega, A. (1999). Breeding and hunting habitat of the Montagu’s Harrier Circus pygargus in La Mata-Torrevieja Natural Park (Alicante, SE of Spain): Effects of habitat structure and prey density. Ardeola. 46(2): 205-212. Close ). A census in Spain in 2006 found 6096–7389 pairs (21 Arroyo, B. E. and García, J. T. (2007). El aguilucho cenizo y el aguilucho pálido en España. Población en 298986 y método de censo. SEO/Birdlife, Madrid. Close ) and 900–1200 pairs estimated in Portugal in mid 1990s (22 Equipa Atlas (2008). Atlas das aves nidificantes em Portugal (1999–2005). Assirio & Alvim, Lisboa, Portugal. Close ). In France, conversion of vole-rich marshes and grasslands to agriculture has decreased the frequency and intensity of vole population peaks, threatening the harrier population that relies on good vole densities for successful reproduction (23 Butet, A. and Leroux, A.B.A. (2001). Effects of agriculture development on vole dynamics and conservation of Montagu’s Harrier in western French wetlands. Biological Conservation. 100(3): 289-295. Close ). Important protection measures adopted in various European countries, particularly France and Spain, based mainly on rescue of nestlings from combine harvesters: chicks moved to safety during harvesting, or small area around nest is left untouched by farmer. Mediterranean populations highly dependent on such measures owing to high nest-failure rates in the absence of intervention (14 Corbacho, C., Sánchez, J.M. and Sánchez, A. (1997). Breeding biology of Montagu’s Harrier Circus pygargus L. in agricultural environments of southwest Spain: comparison with other populations in the western Palearctic. Bird Study. 44(2): 166-175. Close , 24 Arroyo, B., García, J.T. and Bretagnolle, V. (2002). Conservation of the Montagu’s Harrier (Circus pygargus) in agricultural areas. Animal Conservation. 5(4): 283-290. Close , 25 Santangeli, A., Arroyo, B., Millon, A. and Bretagnolle, V. (2015). Identifying effective actions to guide volunteer-based and nationwide conservation efforts for a ground-nesting farmland bird. Journal of Applied Ecology. 52(4): 1082–1091. Close ).