These numbers reflect the abundance of the species near the survey route. They are averages of the total counts along the route for a 5-year period ending in the analysis year (e.g., for the 2015 website, the period covered is 2011-2015). Because each survey route is 24.5 mi long, and consists of 50, 3 minute counts along the length of the route, the abundance estimate represents the number of birds that a very good birder would encounter in about 2.5 hours of roadside birding in the area near the BBS route.