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NEWSLETTER No. 15 -  Summer 1986

WEST MIDLANDS BRANCH, BUTTERFLY CONSERVATION

 

The Art of Pollard Walking

Mention has been made in previous newsletters of the butterfly monitoring scheme initiated by Dr. Ernie Pollard of the Institute of Terrestrial Ecology. This involves weekly walks along a fixed transect in prescribed weather conditions from April to September. Only butterflies seen along this transect are counted and at the end of the season the weekly totals are added together to provide an annual index of abundance for each species. After a few years, trends in site populations can be noted and this can be related to factors such as the weather, changes in management practices, predation etc. The ITE publish an annual report based on data from about 80 sites nationwide, which enables comparison of local findings with the national picture. A transect in Wyre Forest has been walked according to these methods since 1979 and, in more recent years, a number of branch members (and others) have set up transects elsewhere.

We hope that the number of people involved in this method of monitoring will continue to increase. For 1986 it is planned to establish Pollard walks at Nunnery Wood, Worcester and also at Tiddesley Wood near Pershore. Eventually, we hope that all the best butterfly habitats in the region will be monitored in this way. In order to conserve butterflies we need the maximum amount of data on which to base advice and management work. There are a number of sites where we are looking for a willing volunteer to start a transect. If you can help, or you would like to begin a Pollard walk on your favourite butterfly site, contact the Branch Organiser.

I am grateful to those "Pollarders" who have sent in copies of their data; the following observations based on these records will I hope be of interest:

Common Blue - 1985 was a bad year for this species, undoubtedly a reflection of the appalling Summer weather. While the first brood in some sites was about average (the exceptions being the Knapp and Windmill Hill), all sites suffered a serious drop in the number of second generation adults. The species should have benefited, however, from the improved September weather and better breeding success will enable recovery to take place. Nationally, there has been little change in the status of this species over the period of monitoring.
 

Wall Brown - this species nationally has shown a sharp decline over the past 4 years for reasons that are not clear. Normally the second generation is much larger than the first, but in 1985 this was not the case. The national decline has been paralleled locally with a catastrophic fall at Windmill Hill, which is by far the best monitored site for this butterfly, a nil return from the Knapp last year, and not a single record from the Wyre Forest transect since 1983.

 

Marbled White - nationally there has been an almost threefold increase in the numbers of this species at its monitored sites. Most colonies occur on lightly cropped or ungrazed areas of unimproved grassland and can sometimes be very large. In our region conditions at Windmill Hill obviously suit it and, even in 1985, numbers increased on previous years. Sadly the butterfly shows a decrease at the Knapp, possibly due in part to the management techniques used in Papermill meadow (see article). More encouraging is its recent appearance along the edge of Perry Wood.

 

Holly Blue - national data shows this to be a butterfly subject to extreme variation in numbers and this is borne out locally. The last two seasons have been particularly good for the Holly Blue and in a couple of sites it has been recorded for the first time. It is disappointing that none have been recorded on the Wyre Forest transect since 1980. The numbers recorded at Perry Wood are very impressive for a butterfly that is generally only seen in low numbers.

 

Ringlet - this is another species, nationally, which has proved quite a success story over the period of monitoring with a fourfold increase between 1976-84. This figure has been more than matched in Wyre Forest, where, with the exception of 1983, there has been an increase every year. It is another species which favours areas of fairly tall grass and also sheltered situations near woodland or scrub. The pattern of population abundance at Windmill Hill varies markedly from the national trend and this may be due to management practices.

 

The following report from Gareth Lowe demonstrates some of the more detailed comparisons that can be drawn from the data on an individual site basis. In our next newsletter we hope to include a report from Phil Williams on his Pollard walk at Perry Wood.

Mike Williams