The British Isles provide important breeding and wintering sites for a range of bird species. Under the Wildlife and Countryside Act (1981), it is an offence to harm a wild bird or to damage or destroy an active nest. Certain species are afforded additional protection from disturbance through their inclusion on Schedule 1 of this Act. Bird surveys may be required where a development is likely to affect important bird habitats, such as woodland or wetland, or where there is potential for Schedule 1 species to be present.
An appropriate bird survey technique is first chosen based on the objective of the survey and the physical nature of the habitat. The standard technique for surveying breeding birds is based on the British Trust for Ornithology (BTO) Common Bird Census (CBC) and comprises mapping the territories of individual birds using a standard set of symbols. The abundance and breeding distribution of individual bird species can then be assessed. Other survey techniques include point counts, transects, vantage point surveys and Wetland Bird Surveys (WeBS). Where habitats have the potential to support Schedule 1 species, such as barn owls or nightjars, targeted surveys may be required.