You may be interested in some preliminary findings from the KRAG Adders in Decline Project (2003 pilot).
By comparing different refugia (88 tins v 88 roofing felt) at three different Kent sites (Quilters Wood, Kings Wood & Mabledon Hospital) over 58 survey visits, I have calculated the following preliminary results:
% of Total Adder Observations
Basking openly - 8% (only adults)
Roofing Felt - 15% (all lifestages, but only 2 adults)
Tin - 77% (all lifestages)
There are several caveats to these results. Most notably the survey was set up quite late in the season (mid-late June; meaning that animals basking openly upon emergence from hibernation were missed), felt and tins were not always the same sizes etc. However, the results are certainly food for thought and remember it was only a pilot to help plan next year's big project. It certainly looks like roofing felt just doesn't cut it for surveying adders...
I would like to say a big 'Thank you' to everybody who helped set up refugia and/or collect survey results this year. A rough calculation (using current consultancy rates) indicates that this project would have cost over £12000 (on paper)!
I hope many of you will want to help with the main project during 2004! This project will be launched on November 9th at SE Regional HGBI Meeting. A full programme for the conference can be found here.