1.This report provides details of bat surveys undertaken in 2010 at the Sveti Nikola Wind Farm in Kavarna, Bulgaria, on behalf of AES Wind Operations Europe. The report provides a comparison of the results of the 2009 (pre-operation but post-construction) surveys with the 2010 (during operation) surveys. It also provides recommendations for future survey work at the site.
2. Sveti Nikola Wind Farm consists of 52 Vestas V90 wind turbines, constructed over several months during 2009. The area is dominated by agriculture, with arable fields separated by bushy shelterbelts. Operation of the wind farm commenced in spring 2010.
3. Studies from the USA and Europe have found that dead bats can appear in large numbers beneath wind turbines either as a result of collision with the turbine blades or barotrauma, a fatal condition resulting from rapid pressure changes around the turbine. Casualties most often include migrating species, although high-flying resident species are also known to be involved.
4. Commitments were made as part of the original Environmental Impact Assessment (EIA) process and in the subsequent Environmental Management and Monitoring Plan (EMMP) (RSK Group, 2008) to carry out bat activity surveys and bat mortality monitoring to establish if the predicted level of impact was correct. It was predicted that diversity and abundance of bats within the territory would be low and therefore any negative impacts would be ‘within the limits of the admissible’.
5. The surveys carried out in 2009 included ground level car transect surveys both onsite and off-site (as a control) carried out monthly between July and October; bat detector surveys at height carried out during parts of August, September and October; late afternoon observations for foraging migrants during part of September; and nighttime thermal infrared camera and acoustic migration surveys carried out during part of September.
6. The surveys carried out in 2010 included ground level car transect surveys both onsite and off-site monthly between April and October; bat detector surveys at height from April to October; and bat carcass searches (with searcher efficiency and carcass removal trials) carried out from July to October.
7. In 2009 and 2010 a diverse range of bat species was recorded at ground level during the car surveys at the Saint Nikola Wind Farm site. These included, most commonly, Eptesicus serotinus; Hypsugo savii; Miniopterus schreibersii and Pipistrellus nathusii. Species recorded less often were Myotis species; Nyctalus noctula; Pipistrellus BAT SURVEYS 2010 REPORT 80154 - SVETI NIKOLA WIND FARM, BULGARIA 6 RSK CARTER ECOLOGICAL LIMITED pipistrellus; P. pygmaeus; Rhinolophus ferrumequinum; possibly Nyctalus leisleri; possibly Vespertilio murinus and possibly Tadarida teniotis.
8. In both years, no bat species were recorded during the off-site transects that were not also recorded on site (similar diversity) and vice versa. Similarly, bats were no less abundant at parts of the Saint Nikola site than on the transect carried out in more diverse habitats towards the coast (similar abundance).
9. Average numbers of bat passes were higher on site in the summer (during the breeding season) and lower in the autumn (during the migration season) in both years. Average numbers peaked to the north of the site in the autumn and peaks can be seen at the coast in both the summer and the autumn.
10. The patterns in bat activity are fairly similar year to year, although the summer peak in the on-site transects appeared later in 2010 (August) compared to 2009 (July) and the autumn peak in the off-site transects appears earlier in 2010 (September) compared to 2009 (October). It is not known why this pattern occurs although it could relate to ambient temperature, which was higher (compared to 2009) in August and September 2010 than in July and October respectively.
11. In general, higher numbers of Eptesicus serotinus and lower numbers of Hypsugo savii and Miniopterus schreibersii were recorded in 2010 compared to 2009. There was no obvious pattern in the changes observed between 2009 and 2010 for Pipistrellus nathusii.
12. There were numerous technical difficulties with the detectors placed at height and any recordings made included high noise levels from the turbine nacelles. There was no effective data collection during 2010 (during operation) as a result, although several species at risk from wind turbines had been recorded pre-operation during 2009.
13. A single dead Nyctalus noctula was found underneath one of the turbines. No other carcasses were observed during the bat carcass searches, during the trials or during bird carcass searches also carried out at the site. This suggests extremely low levels of mortality here.
14. The car transect surveys and bat carcass searches have commenced in 2011. For this reason, it is proposed that they continue for the remainder of the year to October 2011 but that they cease if no obvious patterns in bat activity emerge and no further bat carcasses are located, regardless of the three year commitment to monitor mortality in the EMMP.
15. This scenario would suggest that the impacts of the Sveti Nikola wind farm on bats in this region are, as expected, low (or insignificant) despite the higher diversity and abundance of bats on site than expected in the original EIA.