Halloween - Not the Only Time to Think About Bats

As we approach Halloween we were thinking about bats and of course bats are an important consideration when you are thinking of installing a wind turbine. Whilst bats are often associated with Halloween, it is in fact a time of year when they are unlikely to be active. The bat survey season is typically from April to September but due to the effects of climate change this has been extended from March until mid October.

Natural England have produced interim guidance about Bats and onshore wind turbines which has been written to assist planners and wind turbine operators when they are considering bats in the wider countryside. In the case of protected sites which are known to be of importance to bat populations more extensive assessments will be needed.

Most bat activity tends to be around close to habitat features where they feed and roost and activity has been shown to be less further away from treelines. To minimise risk to bat populations the Natural England guidelines are to maintain a buffer of fifty metres away from any feature such as trees or shrubs. This means that no part of the turbine should be within that space. The fifty metres should be measured from the blade tip to the nearest feature and not from the turbine tower base.

Most but not all bats tend to fly close to habitat features such as hedgerows, woodlands, walls, rivers and tree canopies. The main objectives of a bat survey are to determine whether the proposed site is used by bats, or is likely to be used by bats at any time of the year. It is important to identify both the species of bat present and the likelihood of there being a significant concentration of bats in the proposed area. Where it is likely or unavoidable that bats could be harmed, alternative sites should be considered.

Bat activity changes at different times of the year so a survey is spread across the season and project planning needs to take this into consideration. Emphasis should be on identifying important flight paths across the site. The surveys include desk studies, searches for maternity roosts, swarming sites or significant hibernation sites near to the proposed turbine location, and bat detector surveys. In high risk areas more visits may be required during key times or there may be increased use of remote detectors.

Many factors influence the site selected for installing a wind turbine but one factor is how it impacts on wildlife. Where any likelihood of harm has been predicted by surveys, this can be minimised by altering the location of the turbine within the site. By ensuring the blade tips are a minimum of fifty metres from the highest part of hedges or woodland nearby bat activity is likely to be so low that there is a very low risk of impact