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The site was identified as internationally important for bird conservation in 2007 because it was regularly supporting significant populations of the species listed below, meeting IBA criteria.

Populations meeting IBA criteria ('key species') at the site:

Species	Red List	Season (year/s of estimate)	Size	IBA criteria
European Nightjar Caprimulgus europaeus	LC	breeding (2004)	365 males	B2, C6
Woodlark Lullula arborea	LC	resident (2006)	220 males	C6
Dartford Warbler Curruca undata	NT	resident (2006)	387 males	C6

Ideally the conservation status of the IBA will have been checked regularly since the site was first identified in 2007. The most recent assessment (2007) is shown below.

State (condition of the key species' populations)
Species	Actual vs Reference (units)	% remaining	Result
European Nightjar Caprimulgus europaeus	365 / 155 (males)	100	favourable
Woodlark Lullula arborea	220 / 67 (males)	100	favourable
Dartford Warbler Curruca undata	387 / 115 (males)	100	favourable

Pressure (threats to the key species and/or their habitats)
Threat	Timing	Scope	Severity	Result
Residential and commercial development	happen­ing now	some of popul­ation/area (10–49%)	moderate deteri­oration (10–30% in 3 gener­ations)	high
Agricultural expansion and intensification	happen­ing now	some of popul­ation/area (10–49%)	slow deteri­oration (1–10% over 3 gener­ations)	medium
Natural system modifications	happen­ing now	some of popul­ation/area (10–49%)	slow deteri­oration (1–10% over 3 gener­ations)	medium
Human intrusions and disturbance	happen­ing now	few individ­uals/small area (<10%)	slow deteri­oration (1–10% over 3 gener­ations)	low

Response (conservation actions taken for the key species and/or their habitats)
Designation	Planning	Action	Result
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

Year	Protected Area	Designation (management category)	% coverage of IBA
1913	Finchampstead Ridges	Nature Reserve (V)	<1
1972	North Wessex Downs	Area of Outstanding Natural Beauty (V)	3
1981	Pamber Forest	Local Nature Reserve (IV)	<1
1982	Hazeley Heath	Site of Special Scientific Interest (UK) (IV)	1
1983	Sandhurst To Owlsmoor Bogs and Heaths	Site of Special Scientific Interest (UK) (IV)	1
1983	Swinley Park and Brick Pits	Site of Special Scientific Interest (UK) (IV)	1
1984	Wasing Wood Ponds	Site of Special Scientific Interest (UK) (IV)	<1
1986	Ockham and Wisley Commons	Site of Special Scientific Interest (UK) (IV)	2
1986	Horsell Common	Site of Special Scientific Interest (UK) (IV)	1
1986	West Minley Meadow	Site of Special Scientific Interest (UK) (IV)	<1
1988	Bramshill	Site of Special Scientific Interest (UK) (IV)	6
1989	Snelsmore Common	Site of Special Scientific Interest (UK) (IV)	1
1993	Ash To Brookwood Heaths	Site of Special Scientific Interest (UK) (IV)	14
1993	Colony Bog and Bagshot Heath	Site of Special Scientific Interest (UK) (IV)	10
1993	Castle Bottom To Yateley Common and Hawley Commons	Site of Special Scientific Interest (UK) (IV)	7
1993	Bourley and Long Valley	Site of Special Scientific Interest (UK) (IV)	7
1993	Chobham Common	Site of Special Scientific Interest (UK) (IV)	6
1993	Whitmoor Common	Site of Special Scientific Interest (UK) (IV)	1
1993	Eelmoor Marsh	Site of Special Scientific Interest (UK) (IV)	<1
1993	Smart's and Prey Heaths	Site of Special Scientific Interest (UK) (IV)	<1
1993	Decoy Pit , Pools & Woods	Site of Special Scientific Interest (UK) (IV)	<1
1994	Greenham and Crookham Commons	Site of Special Scientific Interest (UK) (IV)	2
1994	Pamber Forest and Silchester Common	Site of Special Scientific Interest (UK) (IV)	1
1994	Basingstoke Canal	Site of Special Scientific Interest (UK) (IV)	<1
1995	Chobham Common	National Nature Reserve (IV)	4
1995	Castle Bottom	National Nature Reserve (IV)	<1
1995	Heath Brow	Site of Special Scientific Interest (UK) (IV)	<1
1998	Brentmoor Heath	Local Nature Reserve (IV)	<1
2000	Broadmoor To Bagshot Woods and Heaths	Site of Special Scientific Interest (UK) (IV)	16
2003	Whitmoor & Rickford Commons	Local Nature Reserve (IV)	1
2003	Fox Corner	Local Nature Reserve (IV)	<1
2004	Padworth Common	Local Nature Reserve (IV)	<1
2005	Ockham and Wisley	Local Nature Reserve (IV)	2
2005	Bisley & West End Commons	Local Nature Reserve (IV)	<1
2012	Hazeley Heath	Nature Reserve (IV)	1

Habitat	% of IBA	Habitat detail
Artificial/Terrestrial	-	Forestry plantations
Forest	-	Broadleaved deciduous woodland; Mixed woodland
Grassland	-
Shrubland	-	Heathland
Wetlands (inland)	-	Standing freshwater; Fens, transition mires and springs

Land use	% of IBA
forestry	-
military	-
nature conservation and research	-
tourism/recreation	-
urban/industrial/transport	-

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Recommended citation
BirdLife International (2025) Important Bird Area factsheet: Thames Basin Heaths (United Kingdom). Downloaded from https://datazone.birdlife.org/site/factsheet/thames-basin-heaths-iba-united-kingdom on 06/01/2025.