BTO First Atlas of Breeding Birds in Britain and Ireland: 1968-1972.
The dataset was used to produce the first BTO/IWC Breeding Atlas 1968-72 (Sharrock, J.T.R. (1976) The atlas of breeding birds in Britain and Ireland. T. & A.D. Poyser).
Volunteer (mostly) observers compiled as complete a list as possible of breeding bird species in each 10-km square and noted whether the species was Possibly, Probably or Confirmed as breeding -- a series of standard categories (and codes) were used to specify these, categories which have since, with mostly minor modifications, become a worldwide standard. To make the set directly comparable to the Second Atlas these were converted into S -- Seen (for Possibly Breeding) or B -- Breeding (for Probably and Confirmed Breeding).
All of Britain and Ireland, and for the published book but not NBN, including the Channel Islands. All 10-km squares with more than a very small amount of land were visited. Note that Fair Isle (Shetland) was considered to be one 10-km square even though it actually comprises parts of four squares.
To compile as complete a breeding species list as possible for every 10-km square in Britain and Ireland.
The list and number of species recorded in each 10-km square are as complete as they can be. Clearly those squares visited for less time (especially the more remote areas) are likely to have fewer species recorded and it is the rarer and more elusive species (eg nocturnal) ones which will not be recorded in these circumstances. However the BTO believes that the maps as published are a true representation of the distribution of the species at a national level, while accepting that there will be some gaps in individual squares.
Specific fieldwork was conducted by mainly volunteer observers although professional help was used in some remoter areas.
Observers were asked to visit each 10-km square and record the presence of as many species as they could find and to note whether they were Possibly breeding (column 1) eg seen in the correct habitat, Probably breeding (column 2) eg holding territory, visiting probable nestsite, or Confirmed breeding (column 3) eg seen carrying food, recent fledglings, nest with eggs or young found. The stated objective was to get as many species into column 3 as possible.
The dataset records the maximum category of breeding evidence obtained for each species in each 10-km square (converted to Seen (S) or Breeding (B) see above).
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Looking up... the number of records that can be accessed through the NBN Atlas.Click to view records for the BTO First Atlas of Breeding Birds in Britain and Ireland: 1968-1972. resource.