Background information

Breeding Bird Survey (BBS): Relative Abundance and Breeding Distribution (1993-2012)

These maps indicate the number of birds seen on BBS routes, grouped into categories of relative abundance. Maps are based on mean counts on BBS routes over the interval 1993 to 2012. Maps were provided by Peter Blancher, PhD, Science and Technology Branch, Environment Canada.

Maps were created for 347 species of birds that breed or occur regularly in Canada AND which have been detected on at least 30 BBS surveys in North America over the past 20 years.

BBS Data Included:

Breeding Bird Survey data for the years 1993 to 2012 were used. Data were downloaded from the USGS BBS ftp site ( and include all data from Canadian or continental USA routes, provided that runtype=1 for the year the data were collected (i.e., random route run at appropriate times and dates under acceptable weather conditions; data acceptable for BBS analyses).

BBS Data Analyses:

Total Counts: Counts were summed across stops to arrive at a single Total Count per route per year for each species.

Route Average: If a route was run more than once in a single year under acceptable conditions, those counts were first averaged. Counts were then averaged across years, resulting in a single average count for the species for the route (Route Average for 1993-2012). Zero counts were included in the average (i.e., sum of Total Counts for the route was divided by the number of years with runtype=1).

Degree Block Average: Routes were grouped by degree block (1 degree of latitude by 1 degree of longitude); a single Degree Block Average (birds / rte / yr) was arrived at for each degree block with BBS data coverage. Again, zero counts were included in the degree block average, that is, all routes were included in the average even if they did not have any birds of a given species in any year.

Map Abundance Classes:

A default of 8 abundance classes was applied to each species map, with cut-offs chosen automatically by ArcView using the "Natural Breaks" method. This default was applied if all cut-offs differed by at least 0.1 birds/rte/yr (after rounding to 0.1); if not, then the number of classes was reduced one by one until all classes differed by at least 0.1 birds.