Circus aeruginosus (Linnaeus, 1758)
Family: Accipitriformes > Accipitridae
Seen gliding above reedbeds on broad and slightly raised wings, the Marsh Harrier has become an increasingly common sight, mainly in eastern England.
The Marsh Harrier is a large and bulky bird of prey that feeds on small waterbirds and mammals, caught in the marshes around our eastern coasts. Made extinct in Britain by persecution in the 19th century, the current population has grown from a single breeding group in Suffolk in 1971.
In the last fifty years, the species has doubled the extent of its breeding range, extending north and west with occasional pairs reaching Scotland.
Select a topic for more facts and statistics about the Marsh Harrier
Marsh Harrier identification is often straightforward.
Listen to example recordings of the main vocalisations of Marsh Harrier, provided by xeno-canto contributors.
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Status and Trends
Population size and trends and patterns of distribution based on BTO surveys and atlases with data collected by BTO volunteers.
This species can be found on the following statutory and conservation listings and schedules.
Marsh Harriers became extinct in the UK in 1899 before recolonising from 1927 onwards; the population in the UK peaked at 15 nests in 1958 but then declined again and reached a low point of just one pair in 1971 (Underhill-Day 1998). It has since increased strongly with a mean of just over 400 breeding pairs reported to the RBBP over the five years 2015–2019 (Eaton et al. 2021). There has been a corresponding expansion in distribution with breeding birds now widely spread across Britain although its strongholds remain in the east of England (Balmer et al. 2013). It is now sufficiently widespread to enable short-term BBS trends to be calculated; these show a 36% increase over the most recent 10 year period for which results are available (2008–18) (Harris et al. 2020).
Breeding Marsh Harriers are concentrated in eastern England, but with small outlying populations in the north west and in Scotland, and have recently bred in Northern Ireland for the first time in over 100 years. In winter they are present in many coastal parts of southern and eastern England, and coastal Wales, plus some inland areas such as the Fens and Somerset Levels.
Occupied 10-km squares in UK
|No. occupied in breeding season||249|
|% occupied in breeding season||8.2|
|No. occupied in winter||350|
|% occupied in winter||12|
European Distribution Map
The breeding range of the Marsh Harrier has more than doubled since the early 1990s.
Change in occupied 10-km squares in the UK
|% change in range in breeding season (1968–72 to 2008–11)||+884%|
|% change in range in winter (1981–84 to 2007–11)||+535.3%|
Marsh Harriers were formerly summer visitors but are now recorded consistently year-round.
Information about movement and migration based on online bird portals (e.g. BirdTrack), Ringing schemes and tracking studies.
An overview of year-round movements for the whole of Europe can be seen on the EuroBirdPortal viewer.
Lifecycle and body size information about Marsh Harrier, including statistics on nesting, eggs and lifespan based on BTO ringing and nest recording data.
View number ringed each year in the Online Ringing Report
|Maximum Age from Ringing||13 years 3 months 8 days (set in 2019)|
|Typical Lifespan||6 years with breeding typically at 3 year|
|Juvenile Survival||0.151 (to age 3)|
|Ring size||F (males) G (females)|
|Field Codes||2-letter: MR | 5-letter code: MARHA | Euring: 2600|
For information in another language (where available) click on a linked name
Interpretation and scientific publications about Marsh Harrier from BTO scientists.
Causes of change
The restoration and re-creation of reedbed habitats for conservation of reedbed specialists is likely to have helped Marsh Harriers, although nesting in arable fields has also been important in the recent recovery (Underhill-Day 1998). Other factors which may also have contributed to the increases include the ban on organochlorine pesticide use and reduced persecution from humans (Underhill-Day 1998).
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