The First Atlas of Wintering Birds in Britain and Ireland: 1981/82-1983/84.

Quality Control

The maps as published are considered a true representation of the distribution and relative abundance of each species at a national level during the survey period. There will be some gaps in individual squares, especially for some of the more elusive and rarer species and some bias due to observer intensity.

Method steps

1. Specific fieldwork was conducted by mainly volunteer observers although professional help was used in some remoter areas.Two methods of fieldwork were requested from observers:1) Specific timed visits. An observer visited a 10-km square for a minimum of one hour and was asked to count all the individual birds seen in that time. At the end of the project these counts were standardized to a ‘day’ defined as 6 hours in the field by using a regression of numbers seen on time spent on a species specific basis.2) Supplementary Records. Observers were encouraged to send in any and all records of counts of species from 10-km squares. In particular these records were of species not seen on timed visits and those involving high numbers.The final published maps used the maximum count in a day over all three winters of each species divided into 3 levels such that 50% of positive records were placed in the lowest category (1), 30% in the middle category (2) and 20% in the highest category (3).

This datasets contains data only for the island of Ireland, but is part of the larger Britain and Ireland master dataset held by the British Trust for Ornithology at Thetford, U.K. All 10-km squares within the island of Ireland with more than a very small amount of land were visited.