Searches for Dead Birds in Smøla Wind-Power Plant Area 2012: Annual Report

Report

Title: Searches for Dead Birds in Smøla Wind-Power Plant Area 2012: Annual Report
Authors: Reitan, O.
Publication Date:
January 01, 2013
Document Number: NINA Report 925
Pages: 30
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Document Access

Website: External Link
Attachment: Access File
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Citation

Reitan, O. (2013). Searches for Dead Birds in Smøla Wind-Power Plant Area 2012: Annual Report. Report by Norwegian Institute for Nature Research (NINA). pp 30.
Abstract: 

(The majority of the report is in Norwegian. However, there is an abstract in English.)

 

This report describes the searches for dead birds in the Smøla wind-power plant area (SWPPA) in 2012, and compares the results of the dead birds found with 2006-2011. Included are also a brief description of some challenges in searches for dead birds because of collisions with turbines, and examination of whether the turbine distribution of the dead eagles in 2012 follow a stochastic (random) distribution as in all the previous years.

 

In 2012, searches were carried out at all turbines six times, using a dog, four in the spring (6-8 March, 12-14 April, 29 April–1 May, 21-23 May) and two in autumn (29-30 August, 14-15 November). In addition, 112 turbine searches were carried out at 16 selected turbines the first week in May, as a separate NINA-project. In March–May a total of 376 turbine searches were performed, an increase from 203 in 2011. In each of the years 2007-2010 , the total numbers of turbine searches in the spring (March-15 June) varied between 359 and 473. In spring 2012 the total number of searches was therefore nearly as high as 2007-2010, except for the last part of May and June. In autumn 2012 a total of 136 turbine searches were performed. The same numbers of searches were carried out in 2011, i.e. about 60% of the search effort in the years 2006-2010 in the months September-November. At the searches in 2012 all 65-68 turbines were searched in two-three days. The field work routines in 2012 were identical as in previous years. both during each search day, at each turbine, and when a dead bird was found. Each dead bird discovered was collected as complete as possible, for later examinations. All dead eagles were reported to Statkraft on the day of discovery.

 

In total 15 dead birds were found beneath wind turbines in the six searches in 2012, 11 in March-May, and four in August and November. In addition, six birds were found outside the searches. Among the 21 dead birds there were six dead white-tailed eagles. Three were found as collision victims in March-May, and three were victims between the end of May and August. Two white-tailed eagles were adults, one was in its first year, and three were sub-adults (i.e. between one and five years old) . Besides the white-tailed eagles, seven other species were recorded; one golden eagle, seven willow ptarmigans, two hooded crows, two common snipes, and one of each of raven, greater black-backed gull, and redwing. The searches were focused on finding eagles.

 

There was in total in 2012 carried out 40% more turbine searches in the SWPPA compared with 2011, and with 25% more dead birds found in the searches and in total 40% more dead birds found irrespective of method of discovery. The data strengthen the results from 2011; i.e. birds disappear faster after collision than earlier supposed in the BirdWind project (Bevanger et al. 2011). There may be many causes to the disappearing; e.g. birds cut in several pieces in the collision, and the pieces carried away by eagles, raven, etc. and in parallel scavenged by insects and birds, and decomposed by bacteria and fungus. This implies that the numbers of discovered dead birds therefore depend on the total search effort in each year, both for the whole year and in spring. Two of the six white-tailed eagles were collision victims on the day for search (i.e. in the 21 search days). The results in 2012 strengthen the results from 2011 that a high search effort especially in the vulnerable periods in spring and autumn is important for the precision and the reliability of the monitoring of mortality in turbines.

 

The six dead eagles were found at six turbines, three of them without previously recorded collisions, strengthening the results from the previous years that collisions may occur on all turbines . There was in 2012 a stochastic distribution of collision turbines, as in all previous years.

 

Norwegian Title: Søk etter døde fugler i Smøla vindpark 2012 - årsrapport

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