counting and estimating birds in a flock (getting ready for the CBCs)

This may be useful for folks doing Christmas Bird Counts, who may be unfamiliar with these techniques:

http://www.sibleybirds.com/w/index.php?title=Estimating_numbers

http://manxbirdlife.im/2011/11/15/counting-large-numbers-of-birds/

http://ebird.org/content/ebird/news/counting-101/

 http://ebird.org/content/ebird/news/counting-201/