Dot Distribution Map

http://www.birds.cornell.edu/pfw_fr/Members/ParticipantMap00.htm
A dot distribution map - or dot density map - uses a dot symbol to illustrate certain features of phenomena. Dot maps ultimately rely on certain clusters and scatters to show any sort of visual pattern. Historical dot distribution maps include Fransican monk's Montizon's map that depicts the different administrative districts in France, and John Snow of England's outbreak of cholera map.
The dot distribution map above shows where FeederWatch participants counted birds in the 2000-2001 bird season.