Background information

North American Breeding Bird Survey (BBS): Relative Abundance and Breeding Distribution (1970-2016)

Background Information:

These maps indicate the estimated mean annual index of abundance between 1970 and 2016, within each analytical stratum (state/province/territory intersected with Bird Conservation Regions). The annual indices of abundance are derived from the Canadian Wildlife Service's annual analysis of the BBS data, and represent the predicted mean count from an average BBS route, conducted by an average observer, within each stratum, from 1970 to 2016. Maps were created for all species of birds with population trend estimates from the BBS.

Map Abundance Classes:

A maximum of 7 abundance classes was applied to each species map, with cut-offs defined by the 10th, 20th, 40th, 60th, 80th, and 90th, percentiles of the distribution of mean abundance indices among strata. For species with relatively few strata and/or little variation among strata in mean estimated abundance, there are sometimes fewer classes, if the 6 percentile above do not differ at the 2nd significant digit (e.g., the 10th and 20th percentiles may both equal 0.011 birds).