Data collection for the Connecticut Bird Atlas fell into two types. Most data were collected by volunteer birders and involved sampling across a grid of 601 blocks, following the same system used for the first state atlas (Bevier 1996). We augmented these block data by hiring trained field crews to collect additional data using detailed protocols that were designed to allow the use of occupancy models to predict occurrence patterns and estimate abundance for as many species as possible.

Blocks were created by taking the grid of United States Geological Survey quadrangles and dividing each quad into six. Each block was approximately 9 square miles (3.2 x 2.8 miles) in size. The current project has five more blocks than the first atlas because we created additional blocks for small patches of coastal land and offshore islands that were not included in the first atlas, or that were merged with adjacent blocks.

To simplify project management, we subdivided the state into eight regions, each with approximately the same number of blocks. Each region had a local volunteer coordinator to help manage data collection in that region and to serve as a point of contact for questions about which blocks needed extra work, field protocols, or to answer questions about especially unusual sightings.

Map of Connecticut bird atlas survey blocks, color-coded by survey region.

Individual birders volunteered to lead the survey effort for a given block, but all observers were encouraged to submit observations from any block they wanted to survey. Birders were provided with access to maps of each block that they could print or pull up online in the field. These maps clearly showed the block boundaries, as well as public lands that had been recorded in a data layer developed by the state of Connecticut’s Department of Energy and Environmental Protection. Each block map was available in both “satellite” and “terrain” (similar to a traditional topographic map) view. We also created a data layer showing the block grid that volunteers could download to Google Earth, and use interactively in the field to determine which block the observer was in at any given time.

Birders were asked to study the maps of their block prior to field work, noting any roads, trails, and other landmarks that would help them locate the block boundaries while in the field or help them gain access to key habitats. We also asked them to look for features that indicated different habitats within the block so that they could be sure to visit a diversity of locations and maximize the number of species that they found. To help volunteers assess when they had spent enough time searching a block, we set target levels of survey effort (different for summer and winter), after which a block would be considered sufficiently well surveyed for it to be better for volunteers to focus their effort elsewhere. Throughout the project, we posted regular updates on the atlas blog to help identify blocks that had not received much survey effort. With the help of the Connecticut Ornithologists’ Association, we also ran some special events to encourage a focus on these blocks, such as a friendly competition to encourage birders to visit poorly-sampled parts of the state in January when the incentive to go birding is perhaps lower than at other times of the year.

For more detail on our methods for each part of the atlas, go to this page for breeding surveys, and this page for winter surveys.