Butterfly Monitoring Scheme

[Michael Gochfeld]

Last week Barb Beck wrote a rather elaborate message about the Pollard 
Method and counts. I'll respond here to the first of her "questions", 
which I assume was largely rhetorical:  MIKE GOCHFELD

Barb Beckwrote: ,
"Are the Pollard walks randomly assigned or just in areas where people 
like to walk?  Around here people are just picking places that are 
convenient and nice to walk.  We are trying to do one.

True they are very useful in getting precise information and very good 
data on a very small area.  But are people covering areas which are not 
nice areas to go for a butterfly walk in?   Are volunteers happy 
covering an area with few butterflies or only very common butterflies 
week after week?"

The answer is NO. In Britain the Butterfly Monitoring Scheme began in 
1976 (there was an earlier survey beginning in 1967). It began at the 
Monks Wood Reserve. It has spread in UK, but mainly in the southern part 
of England where there are enough observers (and enough butterflies to 
attract interest and provide data). 

The results are presented in the book by E. Pollard and T.J. Yates, 
MONITORING BUTTERFLIES FOR ECOLOGY AND CONSERVATION published by Chapman 
and Hall. in 1993. 

Chapter 4 deals with sites and site selection.  The sites include

Nature Conservancy Council preserves =51
Local Wildlife or Woodland Trust Preserves =17
Royal Society for Protection of Bird Preserves =13
Forestry Commission sites =7 (I don't know if these are preserves in any 
meaningful sense)
National Trust lands  =4
Local Authorities (parks) =2
Private lands (mainly farmlands) =12

It specifically states that other sites (e.g. suburban gardens) are not 
represented.  There is no evidence that sites are chosen to be randomly 
representative of the countryside.  Rather they would seem to be optimum 
butterfly sites, so that the population trends can be assessed under 
optimal data gathering conditions.  

Sites are visited at least once a week from April thru September.  The 
traditional transect was along a "ride" through woods which seems 
uniquely English.  All butterflies within 5 m in front of the observer 
are counted and no extra attempt is made to dislodge or flush hidden 
butterflies (i.e. beating the bush).

There's more to the method which is worth considering. 

So it is not necessary to organize a count for your local shopping mall 
parking lot, but if you had a count there when it was a "wasteland" 
(i.e. an old field full of flowering plants), then documenting the total 
demise of biodiversity might be worth doing once.  

Mike Gochfeld

 
 ------------------------------------------------------------ 

   For subscription and related information about LEPS-L visit:

   http://www.peabody.yale.edu/other/lepsl