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Sedge Wren	©David Cahlander

A breeding bird atlas is a comprehensive, systematic field survey of the occurrence and distribution of breeding birds, conducted by citizen scientists during a limited time period. Hundreds, often thousands of 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. The Atlas is systematic because 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.

Minnesota's Breeding Bird Atlas
Priority Blocks were selected based on the U.S. Public Land Survey system (link to Where to Survey). There are 2352 Priority Blocks in the state. Each block will be surveyed once during the 5 years of the project; each block survey requires multiple visits to the block during the breeding season. This means we need to cover, on average, about 470 blocks per year.

For most species, MNBBA surveyors will record only breeding evidence for each species they identify. For special species, location, estimates of nests in colonies, and in some cases, a habitat code may be requested. For rare species that occur or breed infrequently in the state, as much detail as the observer can provide will be required. There is a separate, but parallel survey that will provide abundance data (numbers of birds) and additional habitat data. Also, in Minnesota there are large areas that are difficult to accessible. Blocks in these areas will be surveyed by special teams beginning in 2010.