Average Group Size

The FeederWatch “average group size” is calculated by computing the geometric mean of all the FeederWatch counts during the season for a species. This method of calculation takes the flock sizes reported by FeederWatch participants, without including any “zero” counts (counts from FeederWatchers who did not report the species at their site) and uses a formula to compute the mean that de-emphasizes rare high counts to provide a mean that more closely matches what a typical FeederWatcher is likely to see.

The average group size can vary quite a bit depending on the species; those that tend to roam in large flocks (e.g., Pine Siskin) have average group sizes from 1 to over 100, whereas species that tend to feed alone or in pairs in winter (e.g., Downy Woodpecker) are usually seen in much lower numbers.