Initial acoustic surveys were carried out using the following methods:
- Static detectors were placed at height close to the proposed turbine location(s) and set to record for at least five continuous nights
- Two ground-level transect surveys were undertaken using handheld detectors
The continuous monitoring data showed which species were passing through the site, and relative levels of activity throughout the night close to the proposed turbine location. Transect surveys provided further detail on the types of activity and location of any preferred foraging or roosting habitats, or commuting corridors.
Results from the initial surveys were used to determine whether a full season of bat survey data was required to properly assess the risk of impacts to bats. In some cases, where bat activity was particularly low or focused on a certain feature, it was sufficient to adjust the position of the turbine to avoid the risk of impacts (‘micro-siting’). Other outcomes have included:
- Powys, Wales: Initial transects showed high levels of activity by both soprano and common pipistrelles throughout the site but particularly along boundary woodlands and hedgerows. Myotis bats and serotines were also recorded. Analysis of the static monitoring data showed that noctules and lesser horseshoe bats were present but in fewer numbers. Recommendations were made for a full season of bat surveys to build up a complete picture of bat activity on the site prior to exploring possible mitigation measures.
- Norfolk, England: A full season of bat surveys found that common and soprano pipistrelle bats were foraging in moderate numbers within the site, but not were not at risk of turbine impacts. Noctule, serotine and Myotis bats were recorded in very low numbers, foraging outside the turbines’ zone of influence. It was concluded that the development could proceed with a minimal risk of impacts to individual bats or their local conservation status.
- Lanarkshire, Scotland: Scoping surveys found relatively low levels of bat activity focused around tree lines at the site boundaries. A curtailment of operating conditions was agreed whereby the turbine would be switched off during the active season when the wind speed was suitable for bats to be flying, to avoid the possibility of impacts to bats occasionally foraging on site.
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