Subject: Butterflies from the Netherlands

From: "Rolf R. van de Pavert" <[email-masked]>
Date: Wed, 8 Mar 1995 04:16:51 -0500

To   : LEPS-L readers
 From : Rolf van de Pavert <[email-masked]>

 Lectori salutem

 One of the problems I have run into in our Dutch Butterfly Monitoring Project
 is the immense fluctuations in observed butterfly numbers.
 This is caused by fluctuations in both the number of butterflies that are
 present AND the fraction of butterflies actually observed. I am looking for a
 way to correct for the influence of the weather on the number of observed
 butterflies. At the moment only the temperature (centigrade), the windspeed
 (Beaufort) and cloud-cover (in fractions, 1/8) are recorded.
 I did try some very simple methods like arbitrarily choosing 25 degrees as
 the ideal flight temperature (IFT) and adding 5% to the observed number for
 every degree below IFT and subtracting 5% for every degree above IFT. This
 smoothed the flight-curves considerably, but it does seem a very crude
 method. As different species have different temperature-requirements, the IFT
 would have to be different for every (group of) species. The same could be
 done with wind and cloud-cover.
 I'm certain some bright people have already tackled this problem, so I would
 be very interested in your comments.

 Greetings and keep in touch

 ========================================================================
 Rolf R. van de Pavert <[email-masked]>
 Office:                     Home:
 --------------------------  -----------------------
 Statistics Netherland
 Div. LMI: Dept Nature
 PO Box 959                  Meppelrade 13
 2273 XZ Voorburg            2544 XL The Hague
 The Netherlands             The Netherlands
 Tel: 070-3374194            Tel: 070-3673557
 ========================================================================