On Christmas Day 1900, Ornithologist Frank Chapman proposed a “Christmas Bird Census” as an alternative to the annual Christmas Side Hunt, where people engaged in contests to see who could shoot the most birds and bring in the largest pile of feathers. Thanks to his efforts, the first CBC was conducted among 27 birders in 25 count circles ranging from Toronto, ON to Pacific Grove, CA. Total species for the entire count = 90.
Today? – The CBC data is used to monitor trends in species distribution and abundance. An example is the American Tree Sparrow shown above. If you go to the NAS CBC Website it is possible to follow species trend for specific areas: