NABA 4JC

[Ernest Williams]

I agree with everything that Michael Gochfeld says below.  I'll just add
(or emphasize) these points:

1.  The volume of data overcomes some limitations in the quality of the
data.  A student of mine and I have done some analyses that support this
point (in prep.), a point that has been supported for Christmas count bird
data.
2.  The counts provide observations that could not be collected in any
other way and thus are *potentially* useful.
3.  The count procedure is one of many possible designs that let one gather
data from a single area for annual comparisons.  I've conducted 2 such
counts for a number of years, and I conduct them the same way each year, so
the comparisons over time tell me things about the dynamics of the local
lep communities.  This is independent of comparisons to anyone else's count
results.
4.  *Important point*  The butterfly count data are useful for answering a
limited range of questions but not for many, many other questions.  It all
depends on what the questions are.

Ernest Williams


>The NABA 4th of July counts are patterned for better or worse on the
>Audubons Society Christmas bird counts, hence the 15 mile diameter
>circles.   Those counts began about a hundred years ago.  There is now a
>substantial literature on the strengths and limitations of extracting
>"scientific" information from those counts.  With appropriate caveats
>they have proven quite useful in a number of respects.  There are also ,
> breeding bird census routes which were scientifically designed to
>sample bird populations in a repeatable fashion, but these too have
>their limitations.
>
>Ann Swengel has published a number of concise reports (back
>cover of NABA's "American Butterflies") intepreting the 4JC data for
>species such as the Monarch (readily identified by almost all
>participants).  I think one should assume that like any data there are
>quality questions, but that the sheer mass of data, and the long term
>trends they document, makes them worthwhile.  Butterfly censusing is
>more vulnerable to phenology and weather than bird censusing, but
>attempts to make counts comparable from year to year, are being
>encouraged.
>
>M. Gochfeld