Post-construction surveys at operational wind farms are an essential part of the on-going monitoring that all wind farm developers should undertake. The monitoring protocols are recommended in guidelines for wind farm surveys published by Scottish Natural Heritage (SNH 2010)[1] and Natural England (NE TIN069, 2010)[2].
Reasons for Post-Construction Monitoring
Post-construction monitoring is an integral part of wind farm survey protocol and is primarily used to test the accuracy of pre-construction survey methods and assessment and to ascertain whether there are any unforeseen impacts of an operational wind farm on birds and bats. In addition, whilst the methods for wind farm assessment are robust they need to be constantly monitored to keep them up to date.
The methods used in the UK to assess the impacts of collision mortality on bird’s uses a theoretical Collision Risk Model (Band 2005). This model is not flawless and when devised assumed that birds would largely avoid operational wind turbines, in the same way that birds generally avoid other structures such as buildings. The avoidance rates were, at the time, a ‘best guess’ and this is one area in which post construction studies have increased the knowledge of the true effects of operational wind farms on birds.
The original avoidance rates were estimated at approximately 95% for most species however as a result of post-construction studies most have been revised up to between 98% and 99%. There are a couple of exceptions, such as White-tailed Eagle and Common Kestrel, which appear to have worse avoidance rates than other similar species and remain at 95%. In essence for most species this means that the model assumes that between 98% and 99% of flights within a wind farm area will avoid the operational turbines.
Post-construction monitoring will usually involve a repeat of pre-construction surveys as well as completing carcass searches. These searches are very important to show the true number of birds and bats that have collided with the operational turbines.
Carcass Searches
At present surveys involve walking linear transects within a search area around each operational turbine looking for bat and bird carcasses, with surveys normally completed every 7 – 14 days (Drewitt and Langston 2008, Lucas et al. 2000 and Osborn et al. 2000). These methods are very time-consuming, impractical and biased as they rely on visually searching an area that greatly depends on the skills of the observer, the size of the carcass, vegetation cover and topography (Drewitt and Langston 2008).
Bats are generally found within an area half the length of the turbine tower however bird carcasses are found over a larger area; usually up to the length to turbine tip. With the advent of new larger more powerful turbines this can mean search areas up to 9.0 ha, which can take a staggering 9 – 10 hours searching by a trained ecologist. That equates to a single days work just to search one turbine.
A study at operational wind farms in Portugal was completed in 2011 where specially trained dogs were used to search for carcasses. The findings supported previously completed trials and were quite eye-opening in terms of both searcher efficiency and detection rates (Paula et al. 2011). This should also be good news for wind farm operators as increasing efficiency of post construction surveys will have a knock-on effect of reducing costs. The dogs were shown to increase efficiency rates of between 4 and 12 times, therefore increasing the speed of the surveys per turbine and detection rates of almost 100% in all habitat types. Detection rates for human searchers were as low as 10% in tall, denser vegetation.
Dogs really are the way forward for completing carcass searches in terms of both providing a cost effective service to clients and increasing the validity and value of post-construction surveys. This latter point will increase the robustness of pre-construction assessment processes and serve to enhance the‘green’ credentials of renewable energy.
The Future is Bright –It’s Liver and White
Back in August 2011 Turnstone Ecology bought a Clumber Spaniel puppy in order to train her as a specialist search dog for operational wind farms. Named Luna (which was not intended to be short for Lunatic but is quite apt!), she is now 7 months old and we’re waiting for her first season and then search training will begin in earnest. Currently she’s being trained to the whistle and various hand signals but she already covers the ground very well and seems to have a very good nose; mostly for chocolate, plastic or anything chewable! The blog will be kept updated with her progress.
Turnstone Ecology has experience of both pre- and post-construction wind farm studies, including activity and vantage point surveys. We are constantly looking for innovative ways of making the process of planning such developments simpler and more efficient and have recently developed a model (based on Band 2005) that assists us with the Collision Risk Assessment process. This allows for the changes within turbine layout and removal of turbines to be reflected within the output of the Collision Risk Assessment and saves both time and costs within what is always a highly iterative process.
If you are planning a new wind farm project or need some advice or assistance with an operational wind farm we would be delighted to hear from you.Please contact us at info@turnstoneecology.co.uk for further information.
