What is a Breeding Bird Atlas?

Sedge Wren ©David Cahlander
A breeding bird atlas is a comprehensive, systematic field survey of the occurrence and breeding status of breeding birds, conducted by citizen scientists during a limited time period. Hundreds, sometimes more than a thousand volunteers, both professional and amateur, watch and record breeding evidence for birds in selected survey areas. The data collected by these volunteer surveyors provide the information used to create maps that describe which species breed in the state and where in the state they breed. Although the project lasts from 5-6 years, it is still considered a 'snap-shot' in time because it is conducted during a limited number of breeding seasons and it is not based on historical information.

A state Breeding Bird Atlas is comprehensive because it includes survey areas throughout the entire state and includes information on all species found in the state. The Atlas is systematic because critical survey areas, referred to as Priority Blocks, are randomly selected based on a geographic grid system. All Priority Blocks are about the same size (8-10 mi²) and are chosen independent of the habitat present within the block or any other characteristic that could bias the results. Different grid systems have been used by states to define their blocks including DeLorme map pages, U.S.G.S. topographic maps, or the U.S. Public Land Survey System.

Although the emphasis is on finding breeding evidence for as many species as possible in every Priority Block, Atlas projects may collect additional data including information about a species' abundance and habitat requirements. For special, usually rare species, more detailed information about the sighting is often requested.