Stretches of heathland in the South are being given protected status to ensure the survival of rare birds.
Dartford warblers have been spotted using the heathland
Birdwatchers have been praised for helping English Nature map the area crossing parts of Berkshire, Hampshire and Surrey over the past ten years.
Information gathered by the volunteers helped set the boundary for the Thames Basin Heaths special protection area.
"Internationally significant" numbers of woodlarks, nightjars and Dartford warbler use the 13 sites identified.
They are all themselves sites of special scientific interest and include areas of heathland around Sandhurst, Camberley, Aldershot and Yateley.
All are threatened by a continuing decline in lowland heaths, English Nature says.
The new classification gives the areas, many of which are owned by public bodies like the MoD, greater protection from development.
John Eyre, of the Hampshire Ornithological Society, said: "Local planning authorities already consult English Nature about planning applications affecting protected sites.
"Now, they'll need to assess potentially damaging proposals under the European rules."