Explanation of Terms

FeederWatch scientists merge all the FeederWatch data, run the data through a series of editing programs, and summarize the data into two variables for each species: “percentage of sites visited” and “average group size.” Both variables provide an index of species abundance.

The summary tables for the current season reflect observations reported to FeederWatch so far. Because some FeederWatchers report their observations several weeks (or months!) after a count period has passed, these data become more representative of actual bird populations as the season progresses. Early in the season, for example, a small sample size will likely lead to exaggerated estimates of the percentage of sites visited. Average group size, however, is not likely to change much for most species.