• New Atlas of Breeding Birds in Britain and Ireland: 1988-1991
  Most 10-km squares in the UK were covered by the survey, and at least eight tetrads were covered in each square. Summary lists detailing which species definitely bred and which possibly bred in each 10-km square are available. Similar data at the tetrad level are available but these also list the number of pairs recorded for each species in each tetrad and for the 10-km square as a whole. The data are only fully comprehensive at the 10-km square level and not at the tetrad level.
  
• Atlas of Wintering Birds in Britain and Ireland: 1981/82 - 1983/84
  This survey covered most of the 10-km squares in the UK. For each square, the maximum count recorded for each species during the survey period is available. There are no data available at a finer resolution than 10-km squares.
  
• Common Birds Census: 1961 onwards
  Data are available on a site or species basis. For each site, annual summary sheets can be supplied providing a list of the species recorded and numbers of territories for each survey year. There are corresponding habitat folders for each plot containing site maps and vegetation details which can be consulted at the BTO. For each species, indices of population change are available.
  
• Waterways Bird Survey: 1974 onwards
  Data are available in the same format as the Common Birds Census.
  
• BTO/JNCC/RSPB Breeding Bird Survey: 1994 onwards
  This survey monitors the breeding birds of 2,000 randomly selected 1-km squares throughout the UK. Species lists and an estimation of population size are available for each of these squares.
  
• Wetland Bird Survey: 1965 onwards
  Wetland Bird Survey (WeBS) Core Count and Low Tide Count Data are available from the BTO's WeBS Office. WeBS aims to provide a scientific basis for the conservation of waterbird populations with the key objectives being to estimate UK population sizes, monitor trends in numbers and distribution, and identify nationally and internationally important sites. Core Counts are conducted at a wide variety of wetlands throughout the UK, both coastal and inland. Around 2,500 sites are covered annually. Counts are made once monthly, normally on pre-selected dates, concentrating on the winter period, although counts from all months are available for some sites. Counts on estuaries are usually made at high tide when birds are most easily counted at roosts. Low Tide Counts are conducted at most large estuaries in at least one winter every six years, with up to four counts being made through the period November - February. The exposed substrate at low tide is divided into small count areas (sectors) enabling the distribution of feeding and roosting birds to be determined in fine detail. WeBS is a joint scheme of the British Trust for Ornithology, The Wildfowl & Wetlands Trust, Royal Society for the Protection of Birds and Joint Nature Conservation Committee (the last on behalf of the Countryside Council for Wales, Department of the Environment Northern Ireland, English Nature and Scottish Natural Heritage).
  
• Heronries Census: 1928 onwards
  Over 75% of UK heronries are visited each year and the number of occupied nests is recorded. Nest counts are available for each year that the colony was visited.
  
• Ornithological Sites Register: late ‘60s/early ‘70s and 1985/86
  A wide variety of sites were visited in all seasons and details of habitat features and ornithological interest were recorded.  A selection of these sites were re-visited during 1985/86 to note any changes in the habitat or bird species present.  This resulted in the 'Review of Site Changes 1985/86' dataset. OSR provides useful background information for sites of ornithological interest and copies of the original survey cards are available.
  
• Ringing recoveries: 1909 onwards
  The BTO, with support from the Joint Nature Conservation Committee, operates a nationwide ringing scheme involving specially trained volunteers. Subsequent reports (recoveries) of ringed birds are recorded by the BTO. Data are available on bird movements to and from a specific site and in some cases more specialised information e.g. moult record cards are also obtainable.
  
• Nest Record Scheme: 1939 onwards
  This scheme records the breeding success rates of many species of British breeding birds. Data are available on clutch size, brood size etc.
  
• Single Species and Special Surveys
  In addition to the above surveys and sources of data, BTO has data available from its large number of single species and special surveys.

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