Nygård et al. 2010. BOU Proceedings – Climate Change and Birds. http://www.bou.org.uk/bouproc‐net/ccb/nygard‐etal.pdf © 2010 BOU & The Author(s) 1 This paper forms part of the proceedings from the BOU conference Climate Change and Birds . Other papers from these proceedings can be viewed at www.BOUPROC.net . A study of White-tailed Eagle Haliaeetus albicilla movements and mortality at a wind farm in Norway Torgeir Nygård, 1 * Kjetil Bevanger, 1 Espen Lie Dahl, 1 Øystein Flagstad, 1 Arne Follestad, 1 Pernille Lund Hoel, 2 Roel May 1 & Ole Reitan 1 1 Norwegian Institute for Nature Research, NO-7485 Trondheim, Norway 2 Norwegian Water Resources and Energy Directorate, NO-0301 Oslo, Norway *Corresponding author. Email: torgeir.nygard@nina.no The wind power plant on the island of Smøla, western Norway, is currently the largest in Norway; it has 68 turbines with nominal capacity of 2–2.3 MW each, hub height of 70 m and rotor blade radius of 38–41 m,. It was constructed in two phases between 2001 and 2005. Approximately 60 White-tailed Eagle Haliaeetus albicilla territories are found in the whole Smøla archipelago. Before construction there were 13 Eagle pairs holding territories in the wind farm area and within 500 m of it, whereas in 2009 this was reduced to only five. Since 1996, baseline data on the White-tailed Eagle population size and reproduction have been collected. In a post-construction study, 50 fledglings were satellite-tagged during 2003–2009, of which 45 provided more than 80 000 GPS positions in total. In addition to the geographical location, data on altitude and flight speed were provided by the transmitters (Microwave Telemetry, Inc., Columbia, MD, USA). Juveniles of both sexes stayed within the Smøla archipelago during their first winter. Most individuals moved away from the area during spring in their second year (April–May). Females dispersed further than males, often more than 800 km during summer, generally to the north. There was a return movement to the natal area during the second autumn. The same pattern was repeated in the third and fourth years for females, while the males showed more philopatry (Bevanger et al., 2009). From August 2005 to May 2010, four of the satellite-tagged birds were killed by collisions with turbines, of 36 White-tailed Eagles in total, involving 20 adults, nine immatures and seven juveniles. April and May are the months with the highest collision frequencies, with 13 (c. 36%) and nine (c. 25%) of the known fatalities. Risk assessments were performed based on GPS positions during the different months of the year and the age of the birds. The transmitters were programmed to transmit their positions at different intervals. Long time intervals (up to 24 h) were used during winter, 3–6 h during spring and autumn, and 1–3 h during summer. An analysis of moves showed that the birds changed positions on average 15 times per day, using a 100-m difference between positions as an indicator of movement. Every change in position was considered to involve a collision risk when the birds were at Smøla and its archipelago. Moves when they were elsewhere were not considered. Monthly 95 and 50% utilization distributions (UDs) (Worton 1989) were produced using the positions from the Smøla archipelago only, with all birds in each month and age-class pooled. The expected number of moves by each bird was estimated by weighing the number of obtained positions by a factor equal to 15 divided by the pre- programmed number of positions taken for each transmitter and month. The total number of expected moves (Me) was then obtained by summing over all birds for each calendar year and month. Kernel UD (95 and 50%) areas by calendar year and month (Ak95 and Ak50) were produced via ArcView 3.3, by using cross-validation and