Bird atlas

A bird atlas is an ornithological work that attempts to provide information on the distribution, abundance, long-term change as well as seasonal patterns of bird occurrence and make extensive use of maps. They often involve a large numbers of volunteers to cover a wide geographic area and the methods used are standardized so that the studies can be continued in the future and the results remain comparable. In some cases the species covered may be restricted to those that breed or are resident. Migration atlases on the other hand cover migratory birds depict maps showing summaries of ringing and recoveries.

Bird atlases vary in methodology but they always involve spatial (locations) and temporal (time) components. A typical bird atlas project collates data on bird presence or abundance with mapping of this information over a significant geographical region over a well-defined period of time. Data gathered in other efforts, such as breeding bird surveys, may also contribute to atlas projects.

The earliest published mapping of biodiversity in the form of an atlas was completed for the flora of Britain - Atlas of the British Flora (1962) The first bird atlas, the Atlas of breeding birds of the West Midlands, covered Staffordshire, Warwickshire and Worcestershire (England) and was published by Collins for the West Midland Bird Club, in 1970., It built on work done by the Club and its subsequent president, Tony Norris, for its West Midland Bird Distribution Survey, circulated privately in 1951, which mapped frequency of sightings and breeding densities against districts based on the boundaries of Rural District Councils. The British Trust for Ornithology published updated atlases, covering Britain and Ireland, in 1993 and 2013.

The West Midlands atlas influenced and was followed by the 1976 Atlas of Breeding Birds in Britain and Ireland. In the decades that followed a number of atlases have been made all over the world and by 2008 atlases had summarised as many as 27.9 million records of birds gathered by at least 108000 contributors, over an area covering roughly 31.4% of the world's land. While early atlases focused on merely presence or absence of species, and their breeding, there is an increasing trend towards those that indicate abundance or relative abundance.

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