Gastrallus immarginatus is associated with field maple Acer campestre, breeding in the bark of veteran standards or pollards in open situations. Over much of its European range it has been reported from oak and other broad-leaved trees, but it becomes increasingly confined to old, living field maple towards its northern fringes, as in Britain.
Gastrallus immarginatus has been recorded frequently in small numbers from Windsor Forest and Great Park, Berkshire since 1936. In the 1990s a number of populations have been discovered in woodland and parkland locations around Bredon Hill, on the Worcestershire-Gloucestershire border, and at Knole Park, Kent. Field maple is rare at Windsor and Knole Park, but around Bredon there is a large number of field maples in old parks and hedgerows and Gastrallus may occur there as a large dynamic population. The status and distribution of this species in Europe is unknown, although in Germany it is regarded as endangered.
In Great Britain this species is classified as Endangered.
Current factors causing loss or decline
Loss of or damage to host trees through agricultural and other operations.
Poor age structure in field maple populations, leading to a future lack of breeding resource.
Shading of host trees through reduction in grazing or planting of new trees.
Bredon Hill and parts of Windsor Forest and Great Park are SSSIs and part of Bredon Hill is a NNR. Both sites are pSACs.
NE have appointed a part-time liaison officer at Windsor to heighten the Crown Estate`s awareness of conservation issues associated with veteran trees.
Action plan objectives and targets
Maintain all populations at all known sites.
Enhance the population size at all known sites by 2010.
Proposed actions with lead agencies
Policy and legislation
Where appropriate, include the requirements of this species when preparing or revising prescriptions for agri-environment or hedgerow schemes. (ACTION: NE, MAFF)
Implement the 1994 review of Tree Preservation Orders to offer further protection to veteran trees. (ACTION: DETR)
Site safeguard and management
Where possible, ensure that all occupied habitat is appropriately managed by 2008, for example through SSSI or agri-environment scheme management agreements. (ACTION: Crown Estate, NE, LAs, MAFF)
Where it is in the interests of amenity, apply Tree Preservation Orders to protect host trees and woodlands. (ACTION: LAs)
Maintain a suitable age structure within field maple populations at occupied sites, either by planting or, preferably, through encouraging natural regeneration. (ACTION: Crown Estate, NE, FC)
Where possible, ensure that land use around host trees is compatible with their survival and growth, avoiding the use of fertilisers, herbicides, pesticides, ploughing, drainage, or over-stocking. (ACTION: Crown Estate, NE, MAFF)
Ensure that the species is included in site objective and site management statements for all relevant SSSI's. (ACTION: NE)
Consider notifying as SSSI's sites holding key populations of the species, where this is necessary to secure their long-term protection and appropriate management. (ACTION: NE)
Species management and protection
Advise landowners and managers of the presence of the species and the importance of beneficial management for its conservation. (ACTION: NE)
As far as possible, ensure that all relevant agri-environment project officers and members of regional agri-environment consultation groups are advised of locations of this species, its importance and the management needed for its conservation. (ACTION: NE, MAFF)
Future Research and Monitoring
Undertake surveys to determine the status of this species. (ACTION: NE)
Undertake surveys of host tree population structure at occupied sites. (ACTION: NE)
Conduct targeted autecological research to inform habitat management. (ACTION: NE)
Establish a regular monitoring programme for the species. (ACTION: NE)
Pass information gathered during survey and monitoring of this species to a central database for incorporation in national and international databases. (ACTION: NE)
Communications and Publicity
Promote opportunities for the appreciation of the species and the conservation issues associated with its habitat. (ACTION: NE)
Links with other action plans
Originally published in: UK Biodiversity Group Tranche 2 Action Plans - Volume VI: Terrestrial and freshwater species and habitats (October 1999, Tranche 2, Vol VI, p33)