Ernest Williams ewilliam at hamilton.edu
Wed Jul 9 11:51:06 EDT 2003

Clay said it exactly right.  For those who are interested, there's a 
literature on the difficulties - and value - of CBC data.  And 4JC 
(JBC is another abbreviation) data can be used in similar ways to 
help answer selected questions.  As in all studies, though, you have 
to be aware of the limitations of the data.

Here are two articles in the scientific literature that used 4JC/JBC 
count data (the first is one my student Scott Kocher and I put 
Kocher, S.D., & E.H. Williams. 2000. The diversity and abundance of 
North American butterflies vary with habitat disturbance and 
geography. J. Biogeography 27:785-794.
Vandenbosch, R.V. 2003. Fluctuations of Vanessa cardui butterfly 
abundance with El Nino and Pacific Decadal Oscillation climatic 
variables. Global Change Biol. 9:785-790.

So, yes, the kinds of data provided by 4JC counts are messy, but they 
aren't obtainable in any other way, and they do provide evidence to 
help answer some questions.

On a local level, I've run two different counts for a long time - one 
for 18 years and one for 16 years - and they tell me a lot about the 
local butterfly fauna and changes in it (I run the counts the same 
way every year).  These kinds of long-term data sets are probably the 
most valuable.

Ernest Williams
Clinton, NY

>All -
>     Let's not forget that for YEARS the ornithological community derided the
>Audubon Christmas Bird Counts with many of the same arguments that are being
>used against the Xerces / 4JC / NABA / whatever-you-want-to-call-'em Counts.
>However, after 100 years of "CBC count data", the sheer bulk of the
>sightings over the time frame served to overwhelm the non-scientific aspects
>of the data collection and reportage, and serious bird-scientists are mining
>the CBC data for trends, etc.
>     Yes, the 4JCs are a social event, and we stop counting "everything" in
>the afternoons to order focus on the species total in order to "beat" the
>other regional counts.   And yes, my counting technique is certainly
>different from Alex's and MG's, but if I do my counting the SAME way in the
>SAME areas for 10+ years, there is a good chance that any emerging "trend"
>may in fact be worthy of a more rigorous treatment by a "real"
>Looking forward to having fun this weekend in Salisbury, CT,
>Clay Taylor
>Moodus CT
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