Boreal Owl
(Aegolius funereus)

Background Information

logo    Christmas Bird Count (CBC)

The Christmas Bird Count, coordinated by the National Audubon Society and now over 100 years old, monitors the status and trends of winter bird populations through an all-day, annual census conducted by groups of volunteers throughout North America. These data reflect the distribution and numbers of winter birds over time.

The CBC trends presented on this website were provided by David Niven, National Audubon Society. The underlying data for the annual index graphs were also provided by David Niven but the graphs were recreated for presentation on this website. The graph presents the median value (i.e. the best estimate of the annual population index) and the upper and lower 95% credible intervals. CBC results presented here are preliminary findings based on CBC data from Canada and the United States combined (Butcher and Niven, Audubon). These data were analysed as part of the Audubon's State of the Birds report.

Data from CBC complement the BBS by providing results for some species that cannot be monitored in Canada on their breeding grounds. On this website the CBC results were used mainly for those species in Canada that breed in areas not well covered by the Breeding Bird Survey but that spend their winters in the United States and more southerly parts of Canada, where their populations can be monitored by the Christmas Bird Count (CBC).

CBC data on this site are displayed with the permission of Audubon.

For more information on the Christmas Bird Count see:
http://www.audubon.org/bird/cbc/index.html

For Audubon's State of the Birds report see:
http://www.audubon.org/bird/stateofthebirds/

For the background document on how CBC trends were derived see:
Butcher, G.S. and D.K. Niven. Combining Data from the Christmas Bird Count and the Breeding Bird Survey to Determine the Continental Status and Trends of North America Birds. National Audubon Society, www.audubon.org/bird/stateofthebirds/CBID/content/Report.pdf



 
 
 

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Date Modified:
2009-12-01