Connecticut Bird Atlas | Chris S. Elphick

The Connecticut Bird Atlas is a project to map all species of birds that occur in the state of Connecticut. Field work took place between spring 2018 and February 2022, and involved nearly a thousand volunteer birders, who submitted more than 600,000 bird observations.

In December 2025, we released an initial draft version of a new Birds of Connecticut web site, where we have posted results of the atlas project as part of a larger compilation of information about the state’s birds. The current site is not a complete or final version, but ensures that all of the core information collected during the atlas is available for people to view. We also plan to use this draft version as a final opportunity to get birder feedback and review of atlas maps to ensure they do not contain errors.

What the current release contains:

Maps showing block data from the first (1982-86) and second (2018-21) breeding atlases.
Maps showing block data from the first winter atlas (2018-22).
Species lists for each block, accessed from the interactive block map.
Timing (phenology) data for key breeding codes.
Text to provide interpretation and historical context for the atlas data – so far, these have been completed for ~70 species; additional species text will be added in batches as it gets finalized.
Population size estimates for many species based on systematic atlas surveys.

What is planned for future releases?

Adding text for the remaining species is the priority, but we also plan to expand the information for all species. Additional components will include:

More detailed information on timing of occurrence throughout the year. (Frank Gallo is helping us with this, based on the charts in his excellent book Birding in Connecticut.)
Predictive maps of occurrence and relative abundance for common and widespread species.
Detailed information on the occurrence history of rare species. (Phil Rusch is helping with this part on behalf of the ARCC – if you go to the owls, you’ll see a few example species that we’ve already done.)
Eventually, we also hope to add a variety of other historical information to make this site the single go-to place for information on the state’s birds.

What birders can do to help:

A quick check of the species lists for any blocks you surveyed or know well. Remember that others may have recorded species you did not find and that we are only mapping species found during the atlas survey period (spring 2018 – Feb 2022). If you do find an error, please use the reporting form to let us know (link in the legend under each map).
If you helped with the atlas, please also check the list of atlas volunteers to make sure you are listed and your name is spelled correctly. If you see other errors on this list, please help us correct them by email me.

Although we still have a way to go before the entire Birds of Connecticut project is complete, we hope that putting the bulk of the atlas data out into the world where people can use it will benefit the hundreds of birders who have contributed to the project, and anyone else interested in the state’s birds.

If you have other comments on the project web site (especially if you find errors), please email me at chris.elphick@uconn.edu.

As more information becomes available about the release of information, I will update this page. Thanks to everyone (especially the many volunteers who did most of the work!) for your patience as we complete this project.