What is a BBA?

A breeding bird atlas is a grid-based survey used to document the status and distribution of all bird species that breed within a given country, state, or county. Most atlas projects base their survey grid on 7.5-minute USGS topographic maps. For the first Ohio Breeding Bird Atlas, as with many other state atlas projects, survey “blocks” were defined by dividing topographic maps into 6 areas of equal size (approximately 10 sq. miles each). Typically, atlas projects randomly select 1 of these 6 blocks throughout the state and document birds breeding within this block (often referred to as the “priority block”). 

Atlas projects are largely accomplished through the dedication of a network of volunteers. Atlas volunteers typically register for survey blocks and commit to providing adequate survey coverage of their blocks. Surveying a breeding bird atlas block involves documenting the bird species present and recording any evidence of breeding or behaviors that suggest an individual is breeding. A series of codes is used to assign each observation to one of three breeding categories: Possible, Probable, and Confirmed. Survey blocks are generally considered complete when the survey effort reaches a designated time allotment (often 20-25 hours) or a certain percentage of “expected” species have been recorded. Atlas projects typically require 5 to 6 years, but atlas survey periods vary widely in length.


Red-eyed Vireo
photo by Matthew Shumar



Cerulean Warbler
photo by Aaron Boone

Breeding Bird Atlases are usually published in book form consisting of breeding species accounts. These accounts include maps that depict the statewide distribution of observations and the breeding status records. Maps are often accompanied by text that describes a species’ current and historical status and distribution.  Click here to view an example of a species account from the 1st Ohio Breeding Bird Atlas.



The Breeding Bird Atlas concept originated in Great Britain in the late 1960’s and culminated in a tremendous volunteer effort of more than 10,000 contributors who systematically surveyed and documented the breeding birds throughout Britain and Ireland. Other European nations, several African nations, Australia, and New Zealand quickly followed Great Britain with their own breeding bird atlas projects. 

In 1971, the United States initiated its first breeding bird atlas in a single county in Maryland. Massachusetts was the first state to complete a state-wide effort, and today, approximately 40 atlas projects have been completed throughout North America. Six U.S. states and one Canadian province have recently completed or are collecting data for their second atlas effort, approximately 20 years after completion of their first atlas project.


Barn Swallow
photo by Tim Daniel

Breeding Bird Atlases in Ohio


Barred Owl
photo by Tim Daniel

Under the direction of Dan Rice and Bruce Peterjohn, data collection for the Ohio Breeding Bird Atlas began in 1982 and continued until 1987. The success of the first Ohio Breeding Bird Atlas can be attributed to over 500 volunteers who contributed over 30,000 hours of their time. The Ohio Breeding Bird Atlas was published in 1991 and provided a wealth of information about the occurrence and breeding distribution of bird species throughout the state. Twenty-three years after the start of the first Ohio Breeding Bird Atlas, Ohio started its second breeding bird atlas and was the 7th U.S. state to initiate a second atlas. Surveys began in 2006 and are planned to continue through 2011. The Ohio Breeding Bird Atlas II is directed by Paul Rodewald (Ohio State University).


For more information on the second Ohio Breeding Bird Atlas and to view data, click HERE.  Other North American and International Bird Atlas resources can be found HERE.