Marsh warbler  (Acrocephalus palustris)

Following a decline in numbers between 1940 and 1960, the British marsh warbler population reached a stable level of around 100 pairs. This population then underwent a severe decline, until there was just one male recorded in the West Midlands in 1989 (5). A population became established in Kent during the 1970s, which had increased in numbers to 25 by 1993 (5). Habitat loss and climate change may have been factors in the decline during the 1950s and 1960s. Local habitat loss resulting from the activities of water authorities such as bank tidying is likely to have affected the species (3), as is disturbance by birdwatchers and egg collecting, both of which have been recorded. Climate change may continue to affect the population, as this species is at the northern extreme of its range in the UK (2).

Vulnerable sites have wardening schemes in place to prevent egg collecting and disturbance by birdwatchers, in addition most of the former breeding sites in Worcestershire are designated Sites of Special Scientific Interest (SSSIs). The Worcestershire Wildlife Trust has produced management guidelines for rivers, which will be promoted by the Environment Agency in areas where the marsh warbler occurs. The marsh warbler is a priority species under the UK Biodiversity Action Plan (UK BAP), which aims to encourage a long-term expansion of the population in the UK (5).