Marsh Warbler

Listen to example recordings of the main vocalisations of Marsh Warbler, provided by xeno-canto contributors.

This species can be found on the following statutory and conservation listings and schedules.

UK Birds of Conservation Concern	Red listed
Species of European Conservation Concern	Least Concern
IUCN Red List of Threatened Species (global)	Least Concern
Schedule 1 license required (to disturb)	Yes
Birds Directive Annex 1	No
Listed on the Annexes of	WCA(I,IV), Bern(III), Bonn(II), NERC (41)

The breeding population at the start ofthe twentieth century may have been over 180 pairs, with numbers beginning to decline after 1950 (Kelsey et al. 1989). During the 1970s there were around 60–80 pairs of Marsh Warbler breeding in the UK, with the stronghold in Worcestershire (Kelsey et al. 1989). Declines occurred during the 1980s and 1990s and breeding in Worcestershire was last confirmed in 1995, with small numbers subsequently continuing to breed elsewhere in the UK, mostly at east coast locations (Bell et al. 2021). The five-year mean figure reported to the Rare Breeding Birds Panel for the period 2015–2019 was just 10 breeding pairs (Eaton et al. 2021).

Singing Marsh Warblers apperar rather unpredictably and few sites are occupied in successive seasons. The breeding-season distribution map shows a strong bias towards the east coast of Britain, reflecting this species’ easterly direction of arrival from its East African wintering grounds.

Up until the late 1980s, Marsh Warbler distribution was very different, with a regular population in southwest England between Worcestershire and Somerset. From a high of 180 pairs the population dwindled to extinction over 80 years. Subsequently, a small population appeared in Kent but that too disappeared, with disturbance and egg-collecting thought to have contributed to their demise.

% change in range in breeding season (1968–72 to 2008–11)

+128.6%

Marsh Warbler is a rare summer visitor, arriving in mid May. Additionally small numbers are encountered on autumn migration in September.

View a summary of recoveries in the Online Ringing Report.

Foreign locations of birds ringed or recovered in Britain & Ireland

View number ringed each year in the Online Ringing Report

Maximum Age from Ringing

7 years 10 months 22 days (set in 1993)

Wing Length	Adults	70.5±1.7 | Range 67–73mm, N=53
	Juveniles	68.3±1.6 | Range 66-71mm, N=21

Body Weight	Adults	12.9±1.1 | Range 11.4–15.0g, N=49
	Juveniles	12.7±2.3739 | Range 9.75–17.6g, N=20

Feather measurements and photos on featherbase

Ring size	A
Field Codes	2-letter: MW | 5-letter code: MARWA | Euring: 12500

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Causes of change

Habitat changes including fragmentation and natural succession may have made some sites less suitable in the Worcestershire stronghold, but as some suitable habitat remained it is likely that other factors also contributed which may have included disturbance from birdwatchers and egg collectors; additionally the isolation of the population meant that immigration would have been limited and the population would have been more at risk from chance events affecting a large proportion of birds during winter or on migration (Kelsey et al. 1989; Bell et al. 2021). The UK remains at the edge of the species' breeding range and therefore the small remaining population remains vulnerable even though suitable habitat exists.