[Tweeters] statistical rigor in BBS & CBC

Charles Swift chaetura at gmail.com
Sun Jul 23 15:30:39 PDT 2006

Howdy -

The point was made that when it come to sampling methodologies, the BBS
(Breeding Bird Survey) is more rigorous than the CBC (Christmas Bird Count).
This is clearly the case, however, new statistical techniques have been
employed to extract some very useful analyses from the CBC data set. The
104th CBC summary had several very interesting articles with statistically
defensible results based on CBC data. (see for example
CBC has been particularly useful in monitoring some boreal species
nest far to the north of any BBS route.

It should also be mentioned that the BBS does have its own weaknesses and
has been criticized over the years for a variety of problems (such as
observer variability) which may affect the validity of analyses.
Nevertheless it is the only standardized continent-wide survey of breeding
birds and has certainly proved its value. Probably the true strength of
surveys like these is brought out when the data are correlated and
reinforced from multiple sources.

It is the case that both the BBS and the CBC could be improved and there are
efforts ongoing to do this. Howcever, birders should feel comfortable that
their contributions to both the BBS and CBC are important and useful to
science and conservation. (The BBS, by the way, could be greatly helped with
greater coverage aided with the participation of more birders, many routes
do not get run, even in birder rich states like Washington).

thanks, Charles

Charles Swift
Moscow, ID
chaetura at gmail.com

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