What is a Breeding Bird Atlas?
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.
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.