These categories reflect the change in the population of the species relative to circa 1970 (early 1970s) or the closest available time period. This time period was selected as the reference point for assessing population change mainly because there are few data available previous to this period for most species. Population change categories are based on the magnitude and direction of trend and the pattern in the annual indices of abundance over time from the population monitoring program(s) that is considered to provide the best long-term information on the species. Data sources with a longer time series, greater geographic coverage, and more standardized survey methods were preferentially selected. The criteria for decreases and increases in the above table are symmetrical about zero in logarithmic scale and are equivalent in magnitude. For example, a 100% increase (Large Increase) is needed to reverse a 50% decline (Large Decrease).
For more details, please see the "General introduction and methods" section.
The reliability with which the change in population can be determined varies depending on the quality and time period of data available for each species. The reliability of each data source used was assessed in relation to its statistical precision, coverage of the species’ breeding population or range, survey design, and magnitude of the population change. The reliability of the population change category for each species is based on a cumulative assessment of all data sources used.
For more details, see the "General introduction and methods" section.
Understanding the status of bird populations in the context of clear management goals is important to highlight species of concern and to help prioritize the use of limited resources. In 2012, Environment and Climate Change Canada developed quantitative, species-specific population goals for most native bird species in Canada. We developed a variety of goals depending on whether: the species is harvested, distribution changed from historical levels or is very restricted in Canada, abundance declined, and/or if current abundance meets societal and ecological needs. Recognizing that bird populations vary naturally over time and thus some deviation around the goal is expected, we also developed acceptable limits relative to the goal. We assessed the current population of each species with respect to these goals. Under this system, species falling within these limits do not trigger immediate conservation concerns because they are reasonably close to their goals. Species falling below or above their limits are flagged either as possible species at risk or those that may require population management.
