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GCN Survey Project 2004 - Results Summary: |
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calumma Senior Member Joined: 27 Jun 2003 No. of posts: 351  View other posts by calumma |
Posted: 11 Nov 2004 I've written this up on my blog already, but thought that it might be of wider interest. This survey project was run in conjunction with KRAG and BTCV Pond Wardens. Most of the data is now in and I have prepared some preliminary analyses that are very revealing. Some of these numbers can appear a little mind bending at first so stick with me! A total of 125 ponds were assessed during the project (there may be a few additional ponds to add, but the total is unlikely to change too much). Pond wardens and members of KRAG undertook much of the survey work. A large number of ponds were also assessed by David Sewell who is currently studying crested newts as part of his PhD at DICE. Many ponds were assessed in a single visit and the likely presence of crested newts determined through the collection of various habitat variables. Rob Oldham and colleagues at De Montfort University have used these habitat variables to calculate a Habitat Suitability Index (HSI) for crested newt. The higher the calculated value the greater the number of crested newts that are likely to be found in the pond. I use this technique in my work all of the time and find it to be a very useful tool for predicting likely presence of crested newt. However, note that the calculation of a HSI does NOT replace decent survey work!! I have adapted the published HSI slightly to make the results more accessible to my clients (and survey volunteers). Basically, calculated results are grouped into the following categories: Poor Potential Below Average Potential Average Potential Good Potential Excellent Potential Unsuprisingly, crested newts are most likely to be encountered in ponds with a HSI potential of 'good' or 'excellent', although they may also be found in ~50% of the 'average' ponds. Crested newt are rarely encountered in 'below average' ponds and I have never confirmed crested newt from 'poor' ponds. The suitability of ponds for supporting crested newt during the 2004 project was found to be: Poor: 26% Below Average: 18% Average: 22% (but remember that crested newt are only likely to be found in half) Good: 25% Excellent: 9% During this year's project, survey work sufficiently detailed enough to reliably determine the likely presence of crested newt was undertaken in 57 of the 125 ponds. Of the 57 ponds surveyed, we predicted that crested newt would be encountered in 45% of the ponds (9+25+11). To save your brain, 45% of 57 is 26 ponds. So how did we do?! Survey work in 2004 actually confirmed crested newt present in 27 of the 57 surveyed ponds (47%)! This is a little better than expected and I think that everybody involved in this project deserves a very large pat on the back! Hopefully we can run this project again in 2005. If you would like to participate please let me know. I have also identified those areas in Kent where survey work is most needed. For more details follow the link for my blog. Lee Lee Brady Kent Herpetofauna Recorder | Independent Ecological Consultant |
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GemmaJF Admin Group Joined: 25 Jan 2003 No. of posts: 2090  View other posts by GemmaJF |
Posted: 11 Nov 2004 Impressive results indeed regarding the HSI! I suppose now I've applied for a noot licence I better volunteer to do some ponds next year ;0) Gemma Fairchild, Independent Ecological Consultant |
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Vicar Senior Member Joined: 02 Sep 2004 No. of posts: 1181 View other posts by Vicar |
Posted: 12 Nov 2004 Lee, Is there any merit in extending the HSI methodology, coupled with empirical data to make broad population estimates ? I'm thinking of pond area or perimeter etc. Steve Langham - Chairman 
Surrey Amphibian & Reptile Group (SARG). |
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calumma Senior Member Joined: 27 Jun 2003 No. of posts: 351 View other posts by calumma |
Posted: 12 Nov 2004 Rob Oldham's original paper uses the HSI to do just that. Basically the higher the calculated score, the higher the gcn population is likely to be. My own work corroborates this to some degree. However, I prefer to use the technique in two ways: 1) A tool for volunteers to guide survey work. Volunteers can quickly calculate HSIs for a relatively large number of ponds. Based on their results the volunteer surveyors can then focus effort on those ponds where gcn are most likely to be found. We will be testing this next year. The ponds where gcn were expected this year, but for what-ever reason did not show, will be revisited again next year. 2) A tool for myself (working as a consultant) to help justify to a client/LA etc, why a surveyed pond displays a good/poor gcn count. Survey work that fails to confirm gcn in a pond that scores excellent on the HSI may need resurveying. A side effect of the HSI is that it is a very useful teaching tool on training courses. When calculating HSI scores for themselves, volunteers quickly grasp how the different habitat variables can affect gcn occupancy. For those not familiar with the technique, HSI calculations rely on the collection of 10 variables: 1. Location (in Britain) 2. Pond Area 3. Desiccation Rate (years out of 10 that pond dries) 4. Water Quality (subjective assessment) 5. % Shade 6. No. Fowl 7. Fish Population (subjective assessment) 8. No Ponds Within 1km 9. Terrestrial Habitat Quality (I have modified this slightly...) 10. % Macrophyte Cover Reference for Oldham et al: Oldham, R. S., Keeble, J., Swan, M. J. S. and Jeffcote, M. (2001) Evaluating the suitability of habitat for the great crested newt (Triturus cristatus). Herpetological Journal, 10, 143-155. Lee Brady Kent Herpetofauna Recorder | Independent Ecological Consultant |
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Vicar Senior Member Joined: 02 Sep 2004 No. of posts: 1181 View other posts by Vicar |
Posted: 12 Nov 2004 ooh....no depth/volume factor ?? Steve Langham - Chairman
Surrey Amphibian & Reptile Group (SARG). |
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calumma Senior Member Joined: 27 Jun 2003 No. of posts: 351 View other posts by calumma |
Posted: 12 Nov 2004 Nope, none. But my experience with volunteers is that this would be something that is too difficult for them to collect. I record depth as a variable anyway - but usually only as a subjective assessment. I agree that it is important and could write for hours on how it probably affects results... I should also add that I am attempting to develop a similar technique for reptiles. I have some preliminary data, but probably not enough for even preliminary statistics. I will post something about this once I have looked at the data some more. Lee Brady Kent Herpetofauna Recorder | Independent Ecological Consultant |
- GCN Survey Project 2004 - Results Summary |