The first Christmas Bird Count was held on Christmas Day, 1900 -- an alternative to the traditional Christmas Side Hunt where the only birds counted were Quite Dead. The result of these many years of annual bird counts is an incredible database of early winter bird populations.
Counts are done, usually by a group, in a designated area on a specific date between December 14th and January 5th. You do not have to be an experienced birder to participate.
For detailed information, check the Christmas Bird Count website. Check their map of count locations which include who to contact. Participation is free and if you live within a count circle, you may be able to count birds at home.