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Location United Kingdom, South East
Central coordinates 0o 44.53' West  51o 22.08' North
IBA criteria B2, C6
Area 11,030 ha
Altitude 60 - 140m
Year of IBA assessment 2007

Royal Society for the Protection of Birds



Site description The IBA contains several widely separated fragments of what was once an almost continuous block of heathland in the Thames basin. It includes much of the remaining heathland and mire in Surrey, north-east Hampshire and south Berkshire. The habitat mosaics comprise acidic grassland and heathland, and areas of invasive Ulex, Betula, Quercus and Pinus sylvestris. The IBA holds important breeding populations of specialist heathland birds.

Populations of IBA trigger species

Species Season Period Population estimate Quality of estimate IBA Criteria IUCN Category
European Nightjar Caprimulgus europaeus breeding  2004  365 males only  good  B2, C6  Least Concern 
Wood Lark Lullula arborea resident  2006  220 males only  good  C6  Least Concern 
Dartford Warbler Sylvia undata resident  2006  387 males only  good  C6  Near Threatened 

IBA Monitoring

2007 high favourable medium
Population
Good - based on reliable and complete / representative data

Agricultural expansion and intensification livestock farming and ranching (includes forest grazing) - small-holder grazing, ranching or farming happening now some of area/population (10-49%) slow but significant deterioration medium
Agricultural expansion and intensification wood and pulp plantations (includes afforestation) - agro-industry plantations happening now small area/few individuals (<10%) slow but significant deterioration low
Agricultural expansion and intensification wood and pulp plantations (includes afforestation) - agro-industry plantations happening now small area/few individuals (<10%) slow but significant deterioration low
Human intrusions and disturbance war, civil unrest and military exercises happening now small area/few individuals (<10%) slow but significant deterioration low
Natural system modifications other ecosystem modifications happening now some of area/population (10-49%) slow but significant deterioration medium
Residential and commercial development housing and urban areas happening now some of area/population (10-49%) moderate to rapid deterioration high
Residential and commercial development tourism and recreation areas happening now some of area/population (10-49%) slow but significant deterioration medium

Caprimulgus europaeus European Nightjar 155 365 males only 100 favourable
Lullula arborea Wood Lark 67 220 males only 100 favourable
Sylvia undata Dartford Warbler 115 387 males only 100 favourable

Most of site (50-90%) covered (including the most critical parts for important bird species)  A comprehensive and appropriate management plan exists that aims to maintain or improve the populations of qualifying bird species  Substantive conservation measures are being implemented but these are not comprehensive and are limited by resources and capacity  medium 

Protected areas

Protected area Designation Area (ha) Relationship with IBA Overlap with IBA (ha)  
Ash to Brookwood Heaths Site of Special Scientific Interest 1,576 protected area contained by site 1,573  
Bourley and Long Valley Site of Special Scientific Interest 824 protected area contained by site 820  
Broadmoor to Bagshot Woods and Heaths Site of Special Scientific Interest 1,696 protected area contained by site 1,715  
Chobham Common Site of Special Scientific Interest 655 protected area contained by site 651  
Colony Bog and Bagshot Heath Site of Special Scientific Interest 1,130 protected area contained by site 1,127  
Thames Basin Heaths Birds Directive 8,275 protected area contained by site 8,275  

Habitats

IUCN habitat Habitat detail Extent (% of site)
Forest Broadleaved deciduous woodland; Mixed woodland  -
Shrubland Heathland  -
Grassland   -
Wetlands (inland) Fens, transition mires and springs; Standing freshwater  -
Artificial - terrestrial Forestry plantations  -

Land use

Land-use Extent (% of site)
forestry -
military -
nature conservation and research -
tourism/recreation -
urban/industrial/transport -

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Recommended citation  BirdLife International (2014) Important Bird Areas factsheet: Thames Basin Heaths. Downloaded from http://www.birdlife.org on 20/12/2014

To provide new information to update this factsheet or to correct any errors, please email BirdLife