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 out of every 6 of these blocks throughout the state, and then document breeding activity of birds within this priority block.
Atlas projects are largely accomplished through the help and dedication of a statewide network of volunteers that document the breeding status of all bird species encountered. Atlas volunteers typically register to "own" survey blocks, which essentially means that they are responsible for providing adequate survey coverage of their block. Surveying an atlas block typically 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 describe each observation and 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 a minimum of 25 hours) or a certain percentage of "expected" species have been recorded. Atlas projects typically require 4 to 6 years of survey coverage before all priority blocks have been properly surveyed.
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 briefly describes a species' natural history and its historical and current status and distribution.
Click here to view an example of a species account from the 1st Ohio Breeding Bird Atlas.