1044 Southern damselfly Coenagrion mercuriale

European status and distribution

Coenagrion mercuriale is widespread but rare in southern central and south-west Europe, and its range extends to northern Africa. The fairly stable centre of distribution in the south-west of the UK appears to constitute a major European stronghold of the species.

UK status and distribution

In the UK Coenagrion mercuriale occurs mainly in south-west England and in south Wales. It has declined in many places and appears to be present only in low numbers at most of its localities. However, more recently the decline may have ceased, with some evidence of recovery in numbers. Strong populations, numbering hundreds to thousands, occur in Dorset, the New Forest and the Itchen Valley in Hampshire, and on the Pembrokeshire Commons.

View UK distribution of this species.

Site selection rationale

Sites for Coenagrion mercuriale have been selected to include the largest known populations in the main part of the species’ range in south Wales and south-west England, where the prospects for long-term conservation of habitat structure and function are good. Smaller populations occur elsewhere, and the larger of these sites have been selected to provide fuller geographical coverage. Most of the selected sites support Coenagrion populations on wet heaths, and are also selected as SACs for 4010 Northern Atlantic wet heaths with Erica tetralix. Populations associated with chalk rivers are also included within the site series.

Site accounts

• Dartmoor Devon
  A valley mire at 280 m altitude supports a southern damselfly Coenagrion mercuriale population of 20–100 individuals, first discovered on the site in 1998. The stronger population occurs in the northern portion of the mire, where springs feed shallow soakways that flow through wet heath. The southern part of the mire has a higher water table with Sphagnum bog-mosses dominating.
• Dorset Heaths Dorset and Somerset
  This site in south-west England, along with Dorset Heaths (Purbeck and Wareham) and Studland Dunes, represents the Dorset stronghold of southern damselfly Coenagrion mercuriale. The large size of the two cSACs, and a long history of records indicating well-established populations, should ensure the future viability of the small populations that occur here.
• Dorset Heaths (Purbeck and Wareham) and Studland Dunes Dorset and Somerset
  This site in south-west England, along with Dorset Heaths, represents the Dorset stronghold of southern damselfly Coenagrion mercuriale. The large size of the two cSACs, and a long history of records indicating well-established populations, should ensure the future viability of the small populations that occur here.
• East Devon Pebblebed Heaths Devon
  This site holds two relatively small populations representing southern damselfly Coenagrion mercuriale in the south-west of its range in England. These populations occur in wet flushes within the site.
• Gower Commons/ Tiroedd Comin Gŵyr East Wales
  Gower Commons, supporting small populations at two localities, represents southern damselfly Coenagrion mercuriale in south Wales.
• Preseli West Wales and The Valleys
  Representing southern damselfly Coenagrion mercuriale in west Wales, Preseli is one of the strongest populations in the UK, with numbers of adults estimated to be in the thousands and with a long history of records. Conditions on the site, created by its current management, appear to be optimal for this species.
• River Itchen Hampshire and Isle of Wight
  Strong populations of southern damselfly Coenagrion mercuriale occur here, estimated to be in the hundreds of individuals. The site in central southern England represents one of the major population centres in the UK. It also represents a population in a managed chalk-river flood plain, an unusual habitat for this species in the UK, rather than on heathland.
• The New Forest Gloucestershire, Wiltshire and Bristol/Bath area, Hampshire and Isle of Wight
  The New Forest in central southern England is an outstanding locality for southern damselfly Coenagrion mercuriale, with several population centres and strong populations estimated to be in the hundreds or thousands of individuals and with a long history of records. With Preseli, Dorset Heaths and the River Itchen, it represents one of the four major population centres in the UK.

SACs where this Annex II species is a qualifying feature, but not a primary reason for site selection

• Corsydd Môn/ Anglesey Fens West Wales and The Valleys
• Gweunydd Blaencleddau West Wales and The Valleys