Species Action Plan

The marsh warbler is a summer migrant which formerly bred in scattered locations across southern England, but a long-term decline became apparent from the 1950s when there were probably well over 100 breeding pairs. Up until 1980 there were still around 50-80 breeding pairs. Until recently, the main breeding area was in Worcestershire in the Severn and Avon valleys, but this population declined rapidly in the 1980s and no breeding pairs were recorded there in 1989. A few pairs subsequently reappeared (including three pairs in 1993), but none was present in 1994; it is likely that the species will become extinct at this locality. A population became established on the Kent coast in the 1970s and these birds have increased slowly in numbers and range since then, to over 25 pairs in at least four sites by 1993. In addition, several other sites are now occupied in adjoining counties (including seven singing males at one site in 1994) and records of unpaired singing birds are now widespread. Elsewhere in Europe, the marsh warbler breeds mainly in the cool temperate middle latitudes, usually in lowland areas. The population is concentrated in central and eastern Europe and has spread northwards in northern Europe in recent decades.

The marsh warbler is specially protected under Schedule 1 of the Wildlife and Countryside Act 1981 and EC Birds Directive, and is listed on Appendix II of the Bern Convention.

The reasons for the decline in the lower Avon population are not well known but some marsh warbler sites have been lost as a result of vegetation change and riverine channel modification.

Climatic factors have been suggested as a partial cause of the long-term UK decline, since the species occurs at the northern edge of its range here, and breeds only in the warmer southern counties of England. However, many aspects of its ecology are poorly understood and numerous apparently suitable nesting areas have never been occupied.

Geographical isolation has been proposed as a possible reason for the near-extinction of the western population. However, the species has had a fragmented and scattered distribution in this country for many decades.

The marsh warbler is prone to disturbance by birdwatchers and others. The nest is relatively easy to find and a number of incidents of egg collecting have been recorded in the Worcestershire breeding area.

Since the mid 1980s the Worcestershire Wildlife Trust has monitored the size, distribution and breeding habitats of the western population, prevented disturbance or persecution and liaised with landowners.

The Trust has undertaken habitat management on both peripheral and core sites to maintain their suitability, even those which have been deserted.

The Severn Trent Water Authority undertook flood alleviation work in 1985 close to the core breeding area. As part of this work, management was carried out to produce areas of herbaceous vegetation which it was hoped would be colonised by marsh warblers.

Most of the former breeding sites of the marsh warbler in Worcestershire (which include the sites occupied in 1993) have been notified as SSSIs.

Since the reappearance of birds in recent years, the Worcestershire Wildlife Trust has been responsible for drawing up species management guidelines for river managers to be promoted by EA staff. It is hoped that these will also be applied to Kent, and areas where populations become established.

In Kent, little has so far been done for the marsh warbler except that local volunteers have monitored the population and provided information on features of breeding habitat. RSPB staff have also carried out small-scale habitat management.

Robin Wynde, Royal Society for the Protection of Birds Tel:01767 680551

Helen Woodman, Wildlife Trusts

The following LBAPs are working on Acrocephalus palustris:

Originally published in: UK Biodiversity Group Tranche 2 Action Plans - Volume I: Vertebrates and vascular plants (June 1998, Tranche 2, Vol I, p49)

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