- This report presents the results of 90 consecutive days of monitoring and mitigation at Saint Nikola Wind Farm (SNWF) in 2015, its 6th operational year. The continued purpose is to investigate the possible impacts on migrating birds.
- Spatial and temporal dynamics in the numbers of different species passing through the wind farm territory during autumn migration 2015 (15 August to 31 October) are presented. The data from the autumn monitoring in the years 2008 to 2015 are used to investigate the potential change in species composition, numbers, altitude or the flight direction of birds observed in these eight years at SNWF.
- The variations in numbers of species, absolute number of birds, overall altitudes of flight and migratory direction of birds most sensitive to wind turbines do not indicate an adverse effect of the wind farm on diurnal migrating birds.
- The Turbine Shutdown System (TSS) probably contributed to a reduced risk of collision during all years of operation with in infrequent periods of intensive soaring bird migration and provided a safety mechanism to reduce collision risk for single birds and flocks of endangered bird species.
- One juvenile Purple Heron, one Common Swift, one Common Buzzard and one Common Kestrel, were found during 725 searches under all 52 turbines for casualties at an interval of seven days or less.
- The predicted mortality rates by species based on preconstruction data on numbers of migrating birds are not supported by the mortality observed during any of the 6 years of operation of SNWF. The levels of mortality predicted pre-construction have not been recorded during any year of operation. This is largely because ‘worst case’ predictions were based on BSPB (Bulgarian BirdLife partner) data that substantially exaggerated the numbers of migrants passing through SNWF.
- The results to date indicate that mortality at SNWF does not constitute a significant obstacle or threat, either physically or demographically to any of the populations of diurnal autumn migrants observed in this study.