Each block consisted of 1/6 of a USGS 7.5 minute topographic quad. One block of every other quad was selected as a priority block. Of a total of 252 priority blocks, 250 were surveyed. Observations in special areas made during the atlas period were also included. Casual observations were gathered at the quad-level, and thus not mapped by block.
(see handbook for full description & use suggestions)
PO Category - possible breeding evidence
Species (male or female) observed in suitable nesting habitat during its breeding season.
Singing male present.
PR Category - probable breeding evidence
Pair observed in suitable nesting habitat during its breeding season.
Bird or pair on territory, or singing male present on more than one date.
Courtship behavior or copulation.
Visiting probable nest site, or nest building by wrens or woodpeckers.
Agitated behavior or anxiety calls from adult.
Brood patch or cloacal protuberance.
Nest building or excavation of a nest hole.
CO Category - confirmed evidence of breeding
Distraction display or injury feigning.
Used nests or egg shells found. Must be carefully identified, if they are to be accepted.
Female with egg in oviduct. (For banders.)
Recently fledged young or downy young incapable of sustained flight.
Adults entering or leaving a nest site in circumstances indicating occupied nest. To be used for nests which are too high (e.g. the tops of trees) or enclosed (e.g. chimneys) for the contents to be seen.