Western Marsh Harrier

Western Marsh Harrier, Circus aeruginosus

Western Marsh Harrier

Western Marsh Harrier, Austria, April 2008, © Markus Jais


English: Western Marsh Harrier, Eurasian Marsh Harrier
Scientific: Circus aeruginosus
German: Rohrweihe
Spanish: Aguilucho lagunero occidental
French: Busard des roseaux

Taxonomy and Subspecies

Currently two subspecies are recognized [GRIN 2009]:

  • C. a. aeruginosus everywhere except where harterti occurs
  • G. a. harterti northwestern Africa from Morocco to Tunisia.

[Mebs & Schmidt 2006] also mention C. a. spilonotus from eastern asia, but [GRIN 2009] only lists the two subspecies mentioned above.


Length: 48-56 cm
Wingspan: 115-130 cm
Weight: Males 400-670 g, Females 540-800 g

Maximum Age

Almost 17 years in the wild. [Mebs & Schmidt 2006]


Lives in open areas. Only European harrier that regularly breeds in reed beds. In recent years, more nests have been found in agricultural areas, for example in corn fields or fallow land.


Occurs in most European countries. Avoids northern latitudes. In Scandinavia, the species is only found in the south. The Western Marsh Harrier does not breed on Iceland and in Ireland. In the UK, the species is only found in England in the south east, north west and south west. The English population is increasing and expanding, so in the future more areas and maybe even Scotland, Wales and Ireland will be future breeding areas of the Western Marsh Harrier.
In central and southern Europe, the Marsh Harrier is patchily distributed while in eastern Europe the species is often more common (especially in the north east like Poland or Russia).
Outside of Europe, the species occurs from eastern Europe through Asia eastwards to northern Japan.


Birds from central and northern Europe migrate south and spend the winter either in Africa south of the Sahara or around the Mediterranean. Some birds regularly spend the winter the The Netherlands [Mebs & Schmidt 2006]. A female was observed during freezing temperatures and complete snow cover in eastern Austria in January 2013 (pers. observation). This may happen regularly for small numbers as this area is rich with food.
One study involving ringing recovery data of 320 birds showed that Western Marsh Harriers breeding in northern and eastern Europa migrate further away from their breeding areas than Western Marsh Harriers breeding in southern and western Europe. On average males migrated further than females in this study [Panuccio et al. 2013].
Western Marsh Harriers leave central Europe as early as late July but some migrate as late as October. The majority leaves during the end of August and the beginning of September [Mebs & Schmidt 2006]. In spring, Western Marsh Harriers return to central Europe in the 2nd half or March and during April. In Scandinavia, the birds arrive mostly in April.

Breeding and Reproduction

Starts breeding with two or three years.
Like the other European Harries, the Western Marsh Harrier normally builds nests on the ground, mostly in reed beds but also in grainfields or fields with rape. Sometimes, nests are built in willow bushes or even in trees up to the size of 15 meter [Mebs & Schmidt 2006].
Normally 4 or 5 eggs are laid, sometimes only 3 or up to 6. According to [Bauer et al. 2005], up to 8 and in extreme cases up to 12!!! eggs are laid. In those case, maybe the eggs have been laid by more than one female.
The incubation time is 31-38 days and the young stay in the nest for another 3-4 weeks. After that time, the chicks are not yet able to fly but may already leave the nest on foot. They can fly at the earliest with 38-40 days [Bauer et al. 2005]. After that, the young are dependent on their parents for another 2-3 weeks.

Food and hunting

Hunts like a typical harrier from low flight over meadows, reed beds and other open areas. Mostly catches prey on the ground but sometimes also in the air or on water [Mebs & Schmidt 2006].
Preys mostly on small mammals and birds (shorebirds, passerines, ducks and others). Sometimes amphibian or small reptiles are killed, too.


The populations have increased in many European countries with negative trends only in some countries in south-east Europe [BirdLife International 2004].
In many countries the species is a quite common birds if suitable habitat exists. The largest number of pairs can be found in Germany (7,000 ), Poland (6,500 to 8,000), Russia (40,000 – 60,000), Belarus (6,000 – 9,000), Ukraine (7,000 – 12,000) and Hungary (5,200 – 6,700). The European population is a little more than 100,000 pairs [Mebs & Schmidt 2006].
In the UK, the species made a dramatic comeback and the RSPB now gives a number of 360 breeding females [RSPB 2009].


Habitat destruction due to drainage of wetlands is the one of the major threats to Western Marsh Harriers.
In France, lead poisoning been detected as a cause of death for Western Marsh Harriers [Mebs & Schmidt 2006]. The birds feed on waterfowl and other animals that have been shot with lead ammunition. This can lead to the death of the birds as has been demonstrated in many cases for other raptors, like the White-tailed Eagle or the Golden Eagle.
Birds breeding in grain and rape fields are threatened by harvesting machines as harvesting of those fields is often done when the young are still in the nest.


For the Western Marsh Harrier, the conservation of wetlands is very important (and for many other species of birds and animals). Where there still are suitable wetlands, they should be legally protected. Damaged wetlands can be restored.
Birds breeding in agricultural areas can be saved by not harvesting the area around the nest [at least 30×30 meter according to [Mebs & Schmidt 2006] until the young have successfully fledged. The farmers can be compensated for the financial loss. This is also done very successfully for the Montagu’s Harrier.
In order to avoid lead poisoning, lead free ammunition should be used. The best solution for raptors would be to outlaw lead ammunition in Europe.

Status IUCN/BirdLife

Least Concern (LC)

Status Global Raptor Information Network

Lower risk


[Bauer et al. 2005] Bauer, H.-G., Bezzel, E. & Fiedler, W. 2005. Das Kompendium der Vögel Mitteleuropas. Aula-Verlag[BirdLife International 2004] BirdLife International. 2004. Birds in Europe: population estimates, trends and conservation status. BirdLife Interntional. Cambridge, UK. (Western Marsh Harrier species account available at: http://www.birdlife.org/datazone/species/BirdsInEuropeII/BiE2004Sp3399.pdf)

[GRIN 2009] Global Raptor Information Network. 2009. Species account: Western Marsh Harrier Circus aeruginosus. Downloaded from http://www.globalraptors.org on 14 May. 2009

[Mebs & Schmidt 2006] Mebs, Theodor & Schmidt, Daniel (2006). Die Greifvögel Europas, Nordafrikas und Vorderasiens. Kosmos Verlag.

[Panuccio et al. 2013] Panuccio, Michele; Mellone, Ugo; Muner, Lisa (2013). Differential wintering area selection in Eurasian Marsh Harrier (Circus aeruginosus): a ringing recoveries analysis. Bird Study 2013.

[RSPB 2009] RSPB Marsh Harrier species account. 2009. Downloaded from http://www.rspb.org.uk/wildlife/birdguide/name/m/marshharrier/index.asp on 16 May. 2009.


Forsman, Dick (1999). The Raptors of Europe and the Middle East A Handbook of Field Identification. PoyserMebs, Theodor & Schmidt, Daniel (2006). Die Greifvögel Europas, Nordafrikas und Vorderasiens. Kosmos Verlag.

Scott, Don (2008). Harriers – Journeys around the world. Tiercel Publishing. Wheathampstead

Simmons, Rob (2000). Harriers of the World. Oxford University Press. Oxford.


BirdLife Species Factsheet for the Western Marsh Harrier

GRIN species account for the Western Marsh Harrier