Since 2009, AES Geo Energy OOD (AGE) has operated the Saint Nikola Wind Farm (“the Project” or “SNWF”). In 2008/2009 and 2009/2010 surveys of geese wintering in the region reported presence of the Red-breasted Goose (RBG), a globally threatened species. The surveys resulted in the first estimation of the number of geese flying through the wind farm territory and a Collision Risk Model predicting potential RBG mortality of colliding with operating turbine blades (see report for 2009/2010). As a result AGE proposed to have regular winter season surveys during the operation of the wind farm with the application of a radar, in line with provisions of the EMMP and requirements of Bulgarian Ministry of Environment and Waters.
The following main goals were set for the 2010/2011 survey:
1. Record winter bird activity specific to the Project area and evaluate dynamics of the activity between the three observed winter seasons;
2. Ascertain whether there is potential for the operating wind farm to have an adverse effect on the wintering birds (with a particular focus on RBG);
3. To apply mitigation measures in order to reduce mortality predicted by the collision risk model.
The wintering period of the geese in the region started in the middle of December (early January in the Project area) and ceased by the end of February in all three winter seasons including 2010/2011. Greater White-fronted Goose (GWFG) was the most common species recorded and the percentage occurrence of RBG in goose flocks was about 7 %. Greylag Goose was recorded sporadically and in small numbers and was not therefore considered at risk from the Project. Lesser White-fronted goose was not recorded in the wind farm territory for all three winter seasons. The duration of the 2010/2011 winter stay in the study area was similar for both RBG and GWFG with a concentration of over 90% of RBG being seen within 20 days (10 days in January and 10 days in February), corresponding to the coldest period of the winter. These results were similar to those from the 2008/2009 and 2009/2010 winters.
The flight altitudes of the geese from all species observed crossing the Project area were most intensive between 50 and 100 m above ground level. Flight activity of geese was greatest in the morning (7-9h) and, to a lesser extent, evening (16-18h). These findings were also similar in the 2008/2009 and 2009/2010 winters. It is also evident that an increasing propensity for geese to use the Black Sea as a roosting site over the three winters does not create an increasing risk of collision mortality from the Project. Rather, the use of the Black Sea is probably more indicative of increased hunting pressure at ‘traditional’ freshwater lakes forcing birds away from this vital resource. Consequently, more dispersed terrestrial sources of fresh water created by poorer land drainage and snow melt become increasingly important and, along with suitable feeding locations, explicatory of geese movements and distribution.
The monitoring of collision victims did not reveal any mortality of GWFG or RBG in the St. Nikola Wind Farm in the 2010/2011 winter. No intact carcasses or remains of any bird species was found in this period. The results strongly suggest that previous collision risk models based on precautionary measures are unrealistic and that the ability of geese to avoid collision risk is very close to 100 %. In the period Jan 10 – Jan 15 on several occasions the TSS, turbine shutdown system was applied. This may have prevented any geese colliding with turbines and may have contributed to the zero casualty rate.