numbers game or counting- Forgot something

[Michael Gochfeld]

The 15 mi diameter count circle developed by the Xerces Society for the
"Count" was simply adapted from the 15 mi diameter used by the Audubon
Society's Christmas Bird Counts.  It probably wasn't appropriate for winter
birds, and there's no reason to assume it's appropriate for summer
butterflies.

One of the early bird counts (1900), I remember (from reading) was simply
"Central Park" (NYC). I don't know when the Audubons settled on 15 mi.
Probably not until the motor car (auto) became available.

I'm not sure it made much sense for winter birds (and indeed the Christmas
count is too early in the winter to give a good winter snapshot).

However, I am sure it makes little sense for summer butterflying.  When NABA
began to take over responsibility for the count and count summaries, I argued
in vain for a different structure (smaller areas, covered more intensively,
and more frequently made more sense).

As Anne said, we've juggled our circle to include as many prime habitats as
one can squeeze into a circular shape.  If area coverage is the issue, we
ought to be able to adjust the shape as long as the 176 sq mi is not exceeded.

Some counts (e.g. NJ's Greenwood Sanctuary) confine themselves to a much
smaller, bite-sized sanctuary.  Others are amputated by natural boundaries
(Bronx NY is probably only 2/3 of a circle since it doesn't cross the Hudson).

We manage to live with these circles, and after a period of time we get used
to covering them as best we can (focusing mainly on productive habitats
within).

Each count compiler has to judge the reliability of a particular count which
is influenced by short-term weather fluctuations (count day and previous day),
season (wet or dry, early or late), and participants (all experienced party
leaders present this year). Long term trends are hard to evaluate in the short
term, but over 20+ years reliable patterns can appear.  I think the
cross-count analyses, looking at continent-wide patterns are pretty
interesting.

Brief comments are published with the count reports (and could include taxa
not "officially" recognized on the form.  Indeed the form does have room for
write-in's.

Anyway people have tried for decades to extract patterns from the Christmas
Bird Counts or to find a denominator (party-hours is often used) for making
them more meaningful. Critics have countered that "they are unscientific".
The criciticisms wax and wane but the number of counts and participants
grows.   A few people have succeeded in publishing interesting research
results, recognizing that the data are noisy.   Anyway, as a compiler of three
counts I can say they are fun, interesting, worthwhile for me and other
loyalists, even if I don't like the basic method.

 Mike Gochfeld



 
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