The Population trends tool allows you to display estimated annual indices of population size over time, with an optional loess smoothed trend line, for a selected time period and season (note however that trend is only calculated on the entire sampling period at each site). Plots for multiple locations and species can be displayed at once. You can start by selecting a project, and then one or more area, and one or more species (you can select multiple areas or species by holding the CTRL key), as well as the other optional features. For details on display of trends,
click here.
How to read the population trend graphs
The trend above the graph is the estimate of % change per year over the period analyzed. For instance, a trend value of -1.7 % as in our example suggests an estimated population loss of 1.7% every year between 1996 and 2014.
"CI" (Credible Interval) is the range of values within which the true trend falls with a probability of 95%. (Very large CIs are not plotted to avoid distorting graphs.)
An asterisk (*) indicates that the direction of the trend (positive or negative) is correct with at least 95% probability.
The plotted population indices are relative measures of the numbers counted each season.
The population trajectory (blue line in the LOESS Smooth visualization) shows general change in population over time.
