Ornithological atlas data: a review of uses and limitations

Despite being a relatively recent development, the mapping of bird distributions using grid-based atlases has become one of the most frequent forms of ornithological survey. The data generated by ornithological atlases have a number of potential uses which are reviewed in this paper under the following categories: (1) education and recreation, (2) documenting distribution and population for conservation purposes, (3) documenting changes in population and range, (4) providing a framework for survey design, (5) assessing bird-environment associations, (6) generating hypotheses about causes of range change and (7) investigating theoretical aspects of ecology. The strengths and weaknesses of atlas data are considered in each case. We conclude that, despite a number of statistical and methodological problems which need to be addressed, atlases have become an indispensable tool for assessing large-scale patterns of bird distribution and distributional change and for answering a wide range of questions relating to them. They have many applications in ecology and conservation and should be regarded as an essential complement to annual population monitoring schemes and fine-scale studies of bird-habitat relationships.