Background information

Definitions

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 the graph icon next to the geographic area listed.

Time Period indicates the time period from which data are obtained. In some cases, two time periods (long-term and short-term) are reported for a survey. Most landbird surveys referred to on this website are conducted annually. However, others are based on periodic collection of data for a set number of years.

Trend is the estimated percent change in the bird population over the indicated period. The magnitude and direction of the 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 trends differ among surveys and are explained in the footnotes for this table. This particular monitoring effort is intended to enumerate all breeding birds; because it is intended to be a complete count, no estimates of precision are generated.