This report presents results from the searches for dead birds in Smøla wind-power plant in 2011-2013. The results are compared with previous studies of dead birds at the wind-power plant.
The first registrations of dead birds in Smøla started in autumn 2005. Searches started in 2006 and in 2007-2010 there were weekly searches of selected turbines throughout the year. In the period 2011-2013, Statkraft has funded a monitoring program to search for dead white-tailed eagles. The monitoring has been carried out up to six times annually at all turbines.
This report includes a description of the basic issues relating to the registration of dead and injured birds in a wind farm, including what happens to a bird after collision until the search time, challenges in the searches, finding and recording the dead birds, and the importance of search and registration regimes. Various methods to apply, in particular the use of feather search dog, are presented. This dog was used throughout the study period and has shown good search motivation and high security in search results.
During 2011-2013 a total of 1397 turbine searches were conducted, some were carried out in spring and some in autumn. Spring and autumn searches thus provide the opportunity to compare results from the monitoring in 2011-2013 with previous studies. A total of 55 dead birds were recorded in the period 2011-2013; 15 birds in 2011, 21 in 2012 and 19 in 2013. Of these 55 birds, willow ptarmigan and white tailed eagles had most casualties. Eighteen willow ptarmigan and 15 white tailed eagles were found below turbines. In addition one eagle injured by turbines was found outside the wind power plant. During the searches casualties of hooded crow, wheatears, greylag goose, golden plover, redpoll golden eagle common snipe, raven, black-backed gull, redwing gyrfalcon, kestrel, herring gull and one wader spp. were found.
Search effort and eagle casualties detected for 2011-2013 are compared with previous years which had weekly searches throughout the year. In general, the results show a relationship between search effort and eagle casualties detected each year. Of the registered dead white-tailed eagles, 47% were found in spring in 2011-2013, while it was 83% in the spring in the years 2006 to 2010 (range 67-100%).
A total of 56 white tailed eagles are recorded over eight years. The probability of finding dead birds increases with increasing search effort. In addition the detectability of dead birds is dependent on the search method. The years of 2007-2010 had a more intensive search effort than any other year, and thus give the best estimates of dead eagles per year, that is a median of 8 eagles. White-tailed eagle casualties varied from 2 to 11 eagles these years. There are always uncertainties associated with any registration method and search effort and there may have occurred dead eagles that were not detected. Furthermore the number of eagle casualties is also probably influenced by eagle population size, bird activity and meteorological conditions. Such analyses are not included in this project, but this extensive dataset on search effort and bird casualties together with and data from other projects may form the basis for such analyses.