The western marsh harrier is often divided into twosubspecies, the widelymigratoryC. a. aeruginosus which is found across most of its range, andC. a. harterti which is resident all-year in north-west Africa.
C. a. aeruginosus (Linnaeus, 1758) – breeding in Europe and the Middle East to central Asia south Europe, Africa, south Asia; wintering in south Europe, Africa and south Asia
C. a. hartertiZedlitz, 1914 – resident in northwest Africa
A fairly pale adult female (note brownremiges and yellow eye) winters nearHodal (Faridabad district,Haryana,India)Adult male (front), juvenile (behind) and adult female (back), illustration from 1899
The western marsh harrier is 48 to 56 cm (19 to 22 in) in length, has a wingspan of 115 to 130 cm (45 to 51 in) and a weight of 400 to 650 g (14 to 23 oz) in males and 550 to 800 g (19 to 28 oz) in females.[8] It is a large, bulkyharrier, larger than other European harriers, with fairly broad wings, and issexually dimorphic. The male'splumage is mostly acryptic reddish-brown with lighter yellowish streaks, which are particularly prominent on the breast. The head and shoulders are mostly pale greyish-yellowish. Therectrices and the secondary and tertiaryremiges are pure grey, the latter contrasting with the brown forewing and the black primary remiges at the wingtips. The upperside and underside of the wing look similar, though the brown is lighter on the underwing. Whether from the side or below, flying males appear characteristically three-colored brown-grey-black.[9] The legs, feet,irides and thecere of the black bill are yellow.[10]
The female is almost entirely chocolate-brown. The top of the head, the throat and the shoulders are of a conspicuously lighter yellowish colour; this can be clearly delimited and very contrasting, or (particularly in worn plumage) be more washed-out, resembling the male's head colours. But the eye area of the female is always darker, making the light eye stand out, while the male's head is altogether not very contrastingly coloured and the female lacks the grey wing-patch and tail. Juveniles are similar to females, but usually have less yellow, particularly on the shoulders.[9]
There is a rarehypermelanicmorph with largely dark plumage. It is most often found in the east of the species' range. Juveniles of this morph may look entirely black in flight.
The male is characterised by the very clear chestnut brown mantle and the grey secondaries and black outer primaries
This species has a wide breeding range from Europe and northwestern Africa to Central Asia and the northern parts of the Middle East. It breeds in almost every country of Europe but is absent from mountainous regions andsubarcticScandinavia. It is rare but increasing inGreat Britain where it has spread as far as eastern Scotland.[11] In the Middle East there are populations inTurkey,Iraq, andIran, while in Central Asia the range extends eastwards as far as north-westChina,Mongolia, and theLake Baikal region ofSiberia.
The female usually is identifiable by the rather dark plumage except the creamy crown, nape, and throat
Like the other marsh harriers, it is strongly associated withwetland areas, especially those rich incommon reed (Phragmites australis). It can also be met with in a variety of other open habitats, such asfarmland andgrassland, particularly where these border marshland. It is aterritorial bird in the breeding season, and even in winter it seems less social than other harriers, which often gather in large flocks.[16] But this is probably simply due tohabitat preferences, as the marsh harriers are completelyallopatric while several ofC. aeruginosus grassland andsteppe relatives winter in the same regions and assemble at food sources such aslocust outbreaks. Still, inKeoladeo National Park ofRajasthan (India) around 100 Eurasian marsh harriers are observed to roost together each November/December; they assemble in tall grassland dominated byDesmostachya bipinnata andvetiver (Chrysopogon zizanioides), but where this is too disturbed by human activity they will use floating carpets ofcommon water hyacinth (Eichhornia crassipes) instead – the choice of such roost sites may be to give early warning of predators, which will conspicuously rustle through the plants if they try to sneak upon the resting birds[17]
The start of the breeding season varies from mid-March to early May. Western marsh harrier males often pair with two and occasionally three females.Pair bonds usually last for a single breeding season, but some pairs remain together for several years.
The ground nest is made of sticks,reeds and grasses. It is usually built in areedbed, but the species will also nest inarable fields. There are between three and eight eggs in a normalclutch. The eggs are oval in shape and white in colour, with a bluish or greenish tinge when recently laid. The eggs are incubated for 31–38 days and the young birdsfledge after 30–40 days.[18]
It hunts in typicalharrier fashion, gliding low over flat open ground on its search for prey, with its wings held in a shallow V-shape and often with dangling legs.It feeds on small mammals, small birds, insects, reptiles, and frogs.[19][20]
Wintering female hunting nearKolkata (West Bengal, India)Western marsh harrier inEstoniaCircus aeruginosus by Jos Zwarts
The western marsh harrier declined in many areas between the 19th and the late 20th centuries due to persecution,habitat destruction and excessivepesticide use. It is now a protected species in many countries. InGreat Britain, the population was likely extinct by the end of the 19th century. A single pair inHorsey, Norfolk bred in 1911, but by 2006, theRare Breeding Birds Panel had recorded at least 265 females rearing 453 young. It made a comeback inIreland as well, where it had become extinct in 1918.[21]
It still faces a number of threats, including the shooting of birds migrating through theMediterranean region. They are vulnerable to disturbance during the breeding season and also liable tolead shot poisoning. Still, the threats to this bird have been largely averted and it is today classified as Species ofLeast Concern by theIUCN.[1]
Cramp, Stanley, ed. (1980). "Circus aeruginosus Marsh Harrier".Handbook of the Birds of Europe the Middle East and North Africa. The Birds of the Western Palearctic. Vol. II: Hawks to Bustards. Oxford: Oxford University Press. pp. 105–115.ISBN978-0-19-857505-4.
Forsman, Dick (1999).The Raptors of Europe and The Middle East: a Handbook of Field Identification. London: T. & A.D. Poyser.
Snow, David W.; Perrins, Christopher M., eds. (1998).The Birds of the Western Palearctic. Vol. 1 (Concise ed.). Oxford University Press.ISBN0-19-854099-X.
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