Scientifically-designed bird atlases began in the UK in the 1960s. Dozens of bird atlases have been produced since, at scales ranging from counties, to countries, to continents.
For a list of projects in the US, click here. Most projects have focused on breeding birds, but some have tackled winter or migration patterns. Most simply document where each species occurs, but some also estimate abundance. And, while the focus has largely been on documenting distributions, most have also made some attempt to explain the distributions in relation to habitats, land use, and other factors. Increasingly, atlases are being repeated with a primary goal of determining whether and how bird distributions are changing.
Connecticut conducted its first atlas from 1982-86, with the results published in 1994 as the Atlas of Breeding Birds of Connecticut by Louis Bevier. The state was subdivided into a grid of 596 blocks, each of which was visited by volunteer birders to generate a list of species present during the breeding season and to determine how strong the evidence was that breeding occurred within the block. Breeding evidence was assessed by observing birds and assigning their behaviors to pre-defined categories that represent possible, probable, and confirmed breeding. To see data from the first Connecticut breeding bird atlas, go here.
The new Connecticut Bird Atlas will repeat the data collection of the first atlas, but will focus on much more than just breeding birds. In addition to describing breeding distributions, we will collect information on the abundance of each species during summer. We will also repeat the effort during the winter and describe non-breeding distribution and abundance patterns. Lastly, we hope to collect data on patterns of land use during migration periods. By the end of the project, we aim to provide comprehensive information on where each species of bird occurs in the state.