Distribution models were developed for 96 species in the BAM avian database that had occurrences in at least 100 4-km grid cells. Avian occurrence records were obtained from two major datasets: (1) the Boreal Avian Modelling (BAM) point-count dataset; and (2) the North American Breeding Bird Survey (BBS) point-count dataset from USGS. Due to large discrepancies in survey characteristics and species detectability, the focus here was on the occurrence portion of the dataset only. Because the models do not account for detection probability, estimates of population size may not be derived from these results.
To improve the predictive power of the model within the boreal forest region, we included data from neighbouring hemiboreal regions (see map), and where possible, from arctic and mountain regions. Because the core BAM dataset is largely restricted to the boreal forest region, these ancillary data consisted primarily of point-level BBS data with, in some areas, small amounts breeding bird atlas data. BBS data were obtained for the level 3 ecoregions that intersected the combined Brandt (2009 ) boreal/hemiboreal regions. This additional data improved coverage of climate and landcover conditions at species' range limits, thereby providing more opportunities to detect differences in habitat suitability. A total of 117,179 point-count locations were used to summarize species occurrence within 29,059 surveyed grid cells.