Background information


Geographic Area indicates the area from which data are obtained. Note that survey coverage varies and most surveys do not completely cover the entire geographic area indicated. To view annual indices of population change (if available) click on a geographic area.

Time Period indicates the time period from which data are obtained. Most landbird surveys referred to on this website are conducted annually. However, some surveys are based on periodic collection of data for a set number of years. An example is the Ontario Atlas of Breeding Birds in Ontario where data for the first and second atlas were collected during two 5-year periods. In this case the time period is presented as: 1981/85-2001/05.

Annual Trend is generally the mean annual percent change in the bird population. The magnitude and direction of the Annual Trend reflect the vulnerability of the species. Species showing large declines are most vulnerable, whereas species with increasing trends are least vulnerable. The methods for deriving annual trends may differ among surveys and are explained in the footnotes for this table.


Confidence Limits are displayed for some surveys. These indicate a 95% probability that the underlying trend falls between the lower and upper limits indicated. Confidence limits provide a measure of variability for the Annual Trend.

Credible Interval (95%) is displayed for several surveys. This "Credible Interval" is analogous to confidence intervals used in other surveys and is used to estimate the variability around the trend and the indices. For more information see: