Bird migration monitoring in the Saint Nikola Wind Farm, Kaliakra region, in autumn 2017, and an analysis of potential impact after eight years of operation

Abstract

1. This report presents the results of 78 consecutive days of monitoring and mitigation at Saint Nikola Wind Farm (SNWF) in 2017, its 8th operational year. The continued purpose is to investigate the possible impacts of SNWF on migrating birds.
2. Spatial and temporal dynamics in the numbers of different species passing through the wind farm territory during autumn migration 2017 (15 August to 31 October) are presented. The data from the autumn monitoring in the years 2008 to 2017 are used to investigate the potential change in species composition, numbers, altitude or the flight direction of birds observed in these nine years at SNWF.
3. 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.
4. The Turbine Shutdown System (TSS) probably contributed to a reduced risk of collision during all years of operation within 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.
5. Regular searches under operational turbines for collision victims were continued, as in several previous years. In autumn 2017 these searches recorded only casualties, for several species of no conservation concern: four Common Swifts, three Yellow-legged gulls, one Chiffchaff, one Willow warbler, one Common moorhen, one Grey partridge, one Red-backed shrike, one Red-breasted flycatcher and one Scops owl.
6. 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 eight 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.
7. The results to date continue to indicate that SNWF does not constitute a significant displacement/disturbing obstacle or mortality threat, either physically or demographically, to any of the populations of diurnal autumn migrants observed in this study.