Western Marsh Harrier (Circus aeruginosus)

The English name Harrier is derived from the Old English hergian, meaning "to harrass by hostile attacks". The scientific name is derived from the Greek kirkos meaning circle, referring to the harriers' habit of flying in circles. Aeruginosus is Latin for "rusty coloured".

Until recently, often more simply known as the Marsh Harrier. At the time it was considered that there were two subspecies - the Western Marsh Harrier (Circus aeruginosus aeruginosus) & the Eastern Marsh Harrier (Circus aeruginosus spilonotus), the latter found mainly in Asia. The Eastern Marsh Harrier has been reclassified & is now treated as a distinct species, (Circus spilonotus).

Marsh Harriers live in large and dense reedbeds around lakes, marshes & rivers with a strong preference for shallow waters with dense vegetation. They are mainly ground nesting.

Marsh harriers are unusual in diurnal raptors in that they have very good hearing with something of a facial disc similar to the owls. They fly with head pointing downwards, using both sight & sound to locate prey (this occasionally results in injury when they hit things in front of themselves). The facial disc is used to enhance the ability to hear the prey in long grass or rushes, rather than as an aid to hunting in low light conditions.

The Marsh Harrier became extinct in this country prior to the start of the 20^th century from a combination of illegal killing, egg collection & drainage of the reedbed nesting sites. With help & encouragement, from the 1920's a small population was restored & started breeding. Unfortunately, in 50's & 60's due to widespread use of organochloride pesticides (e.g. DDT) the population was decimated again, leaving 1 recorded breeding pair in 1971. Since then the population has increased to around 125-150 breeding pairs in 1997, (mostly in East Anglia), consisting of mainly migrant birds from Holland. Currently, still under threat by illegal killing, habitat loss from land-drainage & disturbance from increased use of nesting sites for recreation. There is some evidence that Marsh Harriers are adapting to the poor traditional habitat situation & now nesting on arable land. The Marsh Harrier, along with the Hen Harrier (Circus cyaneus) & Montagu's Harrier (Circus pygargus), is a species protected by special penalties in the UK. If kept in captivity, it is a legal requirement for them to be ringed & registered.

Marsh Harriers predominantly prey on marsh birds and mammals. They will eat birds' eggs, snakes, lizards, frogs, fish and insects. A Marsh Harrier has been observed drowning its prey, after capturing it on the water, it sat on its prey, almost chest height in water itself, until it was dead. It actually took the prey out of the water once or twice to check that it was dead. Marsh Harriers are prone to having food stolen from them by eagles & other large raptors, including other Marsh Harriers.

Conservation Status

IUCN Red List : Least Concern (LC)
UK : Amber

BTO Data :

Species Code : MR
Longevity Record : 3yrs 9months 14days

Also Called :