Western Marsh Harrier (Circus aeruginosus)

Identification

The Western Marsh Harrier is the largest and most robust of the European harriers, notably distinguished by the absence of a white rump. Sexual dimorphism is marked.

• Adult Male Plumage: The body is predominantly reddish-brown with lighter yellowish streaks, particularly on the breast. The head and shoulders are pale yellowish-grey. The tail feathers (rectrices) and secondary and tertiary flight feathers (remiges) are pure grey, contrasting with the brown forewing and the black primary wingtips. In flight, the male appears distinctly tricolored: brown-grey-black. Its eyes, legs, and the cere of its beak are yellow.
• Adult Female Plumage: The female is almost entirely uniform chocolate-brown. The crown, throat, and shoulders are a conspicuously lighter yellowish or creamy color, with varying contrast. The eye area is darker, making the light eye stand out. She is slightly larger than the male.
• Juvenile: Juveniles resemble females but are generally darker overall, with less contrasting head markings and less yellow on the shoulders. They can be brownish-black with a black throat and crown.
• Silhouette and Flight: It has an imposing silhouette with long, broad wings, often held in a shallow "V" shape during its characteristic low flight over marshes and fields.

Scientific Dimensions and Records (Western Marsh Harrier)

These figures confirm the Western Marsh Harrier as a larger raptor than other harriers, with a notable lifespan in its natural environment.

Song and Calls

The Western Marsh Harrier is generally silent outside the breeding season. However, during courtship displays and when alarmed or disturbed, it emits various vocalizations.

Its calls can include:

• During courtship, the male emits a plaintive, high-pitched "kiiuu" call in flight. The female may accompany him with an "iiuu". Harsh calls, comparable to those of a Common Gull, can also be heard.
• The male's alarm call is a repeated "chakara-chakara", while the female's is a sharp "chiuk-chiuk". A shrill "cui-cui-cui..." may also serve as a warning call.
• A faint "ki-ki-ki" is uttered if an intruder approaches the nest area.
• Sharp whistles and interaction calls are also documented.

Habitat and Distribution of Western Marsh Harrier

The Western Marsh Harrier is a typical raptor of wetland habitats, where it hunts and nests. It prefers large reedbeds, marshes, the edges of lakes and ponds, and slow-moving rivers. It also adapts to agricultural crops (e.g., oil-seed rape, winter cereals) and wet grasslands, as well as abandoned salt marshes and mudflats.

Its breeding range extends across Europe and Northwest Africa to Central Asia and the Middle East. Most populations are migratory, wintering in sub-Saharan Africa and South Asia. Migration generally begins in August and birds return in April. It can be found up to 2000 meters (6500 ft) altitude in Asia and 3000 meters (9800 ft) in its wintering grounds in Africa.

Distribution Map

Diet

The Western Marsh Harrier is an opportunistic and carnivorous predator. Its diet is varied and adapts to the available resources in its habitat.

It primarily feeds on:

• Small mammals, particularly rodents (voles).
• Small birds and their chicks or eggs, including waterbirds.
• Amphibians, such as frogs.
• Reptiles, such as lizards and small snakes.
• Large insects, especially orthopterans (grasshoppers, locusts) and beetles.
• Sometimes fish.

It hunts by flying slowly and low (generally between 3 to 5 meters / 10 to 16 ft high) over reedbeds, marshes, and fields, using its keen eyesight to spot prey. Once a target is sighted, it drops silently to seize it with its talons.

Reproduction

The breeding season for the Western Marsh Harrier generally begins in April or May. It is the earliest breeding harrier species. Birds typically reach sexual maturity around three years of age.

• Nest: The nest is built primarily by the female, directly on the ground or very low in dense, tall vegetation, such as reedbeds, marshes, or crops. It is a crude platform made of reeds, rushes, grasses, and twigs. The species may nest in solitary pairs or in small, loose colonies.
• Eggs: The female typically lays 3 to 8 eggs (most often 3 to 5), which are pale, bluish, or greenish, sometimes speckled with brown. Incubation is mainly carried out by the female and lasts approximately 30 to 38 days. The male is responsible for providing food during this period.
• Raising the Young: Chicks are altricial, meaning they are born blind and featherless, completely dependent on their parents. They fledge after 35 to 40 days (sometimes up to 56 days) and remain dependent on adults for several more weeks after their first flight. Male Western Marsh Harriers are often polygamous (25-30% of nests, usually bigamous).
• Courtship Display: The male performs spectacular aerial displays to attract the female, including steep climbs and dives.

Conservation Status

The Western Marsh Harrier is classified as "Least Concern" (LC) by the IUCN (International Union for Conservation of Nature) globally. Its global population size is estimated between 415,000 and 765,000 mature individuals and appears to be increasing. It is a protected species in many countries.

However, this classification masks local concerns, and the species has experienced significant declines in the past. The main threats to the species are related to human activities:

• Habitat Destruction and Degradation: Drainage and drying out of wetlands (reedbeds, marshes, lakes) constitute a major threat, as well as habitat loss due to conversion to crops or urbanization.
• Toxic Products: The use of pesticides and rodenticides in agriculture affects the species and its prey.
• Disturbance: Human disturbances, particularly by fishermen, and predation by foxes near nests are other factors.
• Illegal Shooting and Hunting: Although the threat of hunting has decreased, illegal shooting persists locally.
• Wind Energy: The development of wind energy poses a new threat to the species.

Conservation efforts, including habitat protection and legal measures against hunting, have helped stabilize or increase some populations. The population in the UK, for instance, has seen a significant recovery after near extinction.

Frequently Asked Questions (FAQ)

References

1. Wikipedia - Western marsh harrier