To facilitate analysis of bird records in relation to habitat types, all sites in the bird record database have been assigned to one of 37 topographical areas grouped into six broad classes: Downs, heathlands, river valleys, the Eastern plain between Reading and Windsor and the urban areas.
D1 Lambourn Downs; D2 Farnborough Downs; D3 Compton/Aldworth/Ilsley Downs; D4 Eastern Downs and woods; D5 North Hampshire Downs, Hungerford; D6 North Hampshire Downs, Combe, Walbury heights; D7 Remenham/Hurley/Cookham Plateau.
Heath, heathland woods and associated areas
HW1 Wickham Heath; HW2 Snelsmore Plateau; HW3 Bucklebury/Curridge/Hermitage Plateau; HW4 Inkpen Plateau; HW5 Greenham/Crookham Plateau; HW6 Wasing/Burghfield Commons; HW7 Yattendon/Frilsham; HW8 Crowthorne/Finchamstead; HW9 Swinley Forest; HW10 Windsor Great Park
P1 Twyford/Binfield/Windsor plain
R1 Kennet west of Newbury and Dun; R2 Lambourn; R3 Lower Kennet and tributaries;R4 Pang Valley and Sul Gap; R5 Thames: Goring Gap to Reading; R6 Thames: Reading to Wargrave; R7 Thames Valley: Remenham to Maidenhead; R8 Thames: Jubilee River to Windsor; R9 Thames: Lower Thames and Colne; R10 Loddon/Blackwater Valley: Blackwater; R11 Loddon/Blackwater Valley: Loddon valley above Winnersh; R12 Loddon/Blackwater Valley: Lower Loddon.
U1 Hungerford; U2 Newbury and Thatcham; U3 Greater Reading-Wokingham; U4 Bracknell and Ascot; U5 Maidenhead; U6 Windsor; U7 Slough.