Background information

Atlas of the Breeding Birds of Ontario (2001–2005)

Two breeding bird atlases have been conducted in Ontario, the first between 1981 and 1985 and the second between 2001-2005. During an atlas, the province is divided into grids to which volunteers are assigned and are asked to collect information on the birds breeding in that grid.

Ontario Atlas change statistics reported on this website were provided by Dr. Peter Blancher, Science and Technology Branch, Environment Canada. These statistics are based on data collected for the first and second Ontario Breeding Bird Atlases, and are reported in the second atlas (Cadman et al. 2007).

Changes in atlas breeding evidence measure changes in probability of occurrence, not relative abundance. Change between the first and second atlas was calculated as the proportional change in atlas squares with breeding evidence over the full 20 years. This overall change was converted to an annual % change.

For more information on the Atlas of the Breeding Birds of Ontario, 2001-2005 see:


  • Cadman, M.D., D.A. Sutherland, G.G. Beck, D. Lepage, and A.R.Couturier (eds). Atlas of the Breeding Birds of Ontario, 2001-2005. Bird Studies Canada, Environment Canada, Ontario Field Ornithologists, Ontario Ministry of Natural Resources, and Ontario Nature, Toronto, xxii + 706 pp.