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For many Nebraska birders, the last big event of the year is the Audubon Christmas Bird Count, which is held annually during the last week of December. It is an occasion to join with friends in a day out to try see as many species as possible in a single day. More importantly, it provides a database that, combined with those of more than 50,000 other observers, provides a highly documented population sample of early-winter birds throughout North America, Latin America and the Caribbean region. The tradition began in 1900, and as of 2011 there have been 111 national counts. Nebraska counts began in Lincoln and Omaha in 1909. In recent years there have usually been about 10 counting locations in Nebraska, with notably long sequences having developed in Lincoln, Omaha, Scottsbluff and at Lake McConaughy. This last-named location invariably has the highest state count, often tallying about 100 species, whereas species counts from Lincoln and Omaha are usually in the 70s (Johnsgard, 1998). Since 1988, The Great Backyard Bird Count has attempted to measure February birds, with an emphasis on species likely to be seen in backyards and near homes. During the 2011 counts in Nebraska, 105 species and over 300,000 birds were counted.
Four years ago I decided that I could exploit the Christmas count’s vast amount of population data to test the idea that moderating winter climates in the Great Plains during the past half-century may have resulted in a northward shift of early-winter bird populations. I chose about 200 bird species known to winter in the Great Plains and selected a 40-year period from the winters of 1967-68 to 2006-07 for my study.