Mikkola, H. 2014. Global Warming and Great Grey Owls. Tyto 3/2014:7-8

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Mikkola, H. 2014. Global Warming and Great Grey Owls. Tyto 3/2014:7-8
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    TYTO March 2014 THE INTERNATIONAL OWL SOCIETY   Contents   Page 7-8 ~Global Warming and the Great Grey Owl-Dr Heimo Mikkola Global Warming and Great Grey Owls- by Dr Heimo Mikkola During the past decade, ample evidence has been  presented on the effects of climatic changes on birds  populations. However, most attention has been on the direct effects of climate changes on species of lower trophic levels and mainly on the negative consequences of climate change. The Great Grey Owl is one of the apex predators which is well adapted to live in cold environments, and therefore might reasonably be expected to decline in abundance as a result of rising temperatures. However, with warmer spring weather Great Grey Owl has expanded lately its distribution further south in Fenno-Scandia and in eastern Central Europe. So obviously there is very little understanding of climate change impacts on owls in boreal environments. For some reason it was always thought that in Europe the Great Grey Owl is a bird of high north, moving southwards from Lapland only during the cold periods. In Finland between 1954 and 1981 the Great Grey Owl has bred in all parts of the country, except in the treeless regions in Lapland and in a narrow coastal belt in the most south-westerly part of Finland (Mikkola 1981) The fact that the Great Grey Owl became more common in Finland from 1954 to 1981 was believed to depend on climate change. Interestingly we thought the climate getting colder from 1954 to 1981. Global warming news started to roll in only in the1990s.  In 1992 I concluded that Great Grey Owls range in Finland has extended southwards since about 1930 (Mikkola 1992). Nowadays the Great Grey Owl has expanded its distribution even further south in Norway, Sweden, Estonia, Latvia, Poland, Belarus and Ukraine. In Norway the Great Grey Owl used to breed between 68 and 70˚N but since 1997 nests were found in SE Norway between 60 and 62˚N (Berg et al. 2011). In 2011, 2012 and in 2013 even 29 nests were found in SE Norway. In Sweden most southern nest was found in 2012 at 56- 57˚N (Stefansson 2013). After more than 100-years gap, Great Grey Owl breeding was again confirmed in Estonia 2009, and there were seven further records in 2011. In Latvia, a stationary pair was recorded in 2006-07 and a territorial male was seen 2009 (Ławicki et al. 2013). In 2007-09, the species was found in Belarus near the Polish border, clearly south-west of its regular breeding grounds. In Poland very southern nests wer  e found in 2010 between 51 and 53˚N, and in 2012 eight pairs were found. Thus far the most southern nests in Europe have been found after 2002 in the Kiev region of Ukraine, between 50 and 51˚N, and the current population in the country has been estimated at 60- 110 pairs (Ławicki et al. 2013). 8 These new observations demonstrate since 2007 the clear westward and southward range extension of the Great Grey Owl in Europe. This trend goes definitely against the expectation that global warming would drive northern and eastern species to further north and east. If this expansion trend continues also in the future, then it is only matter of time until the first Great Grey Owls will reach Germany. Old growth spruce forests, for instance in Bayerische Wald, would definitely serve as an ideal breeding biotope for this large owl. It is interesting that at the same time there appears to be little or no evidence of any southward expansion in European Russia or in North America (Alexander Sharikov and James Duncan in litt  .). So maybe this move to west- and southwards is happening only in Western Europe where the last few harsh winters in the north have been mentioned as one possible explanation (Ławicki et al. 2013). At the same time global warming is advancing in the north at the very high rate forcing the Great Grey Owl to adapt itself ever warming springs and summers. This must be as controversial to the owls themselves as for the researchers. Anyhow, a deeper understanding of how climate change affects top trophic level predators is vital, as they are keystone species that can have a disproportionate effect on ecosystems. However, studying survival and distribution in an apex predator, like the Great Grey Owl, requires individual- based data from long-term studies and is complicated by the integration of climatic effects on prey species at lower trophic levels.  References  Berg, T., Solheim, R., Wernberg, T. & Østby, E. 2011. Lappuglene Kom! Vår Fuglefauna 34: 108-115.  Ławicki, Ł., Abramčuk, A.V., Domashevsky, S.V.  , Paal, U., Solheim, R., Chodkiewicz, T. & Woźniak, B. 2013. Range extension of Great Grey Owl in Europe. Dutch Birding 35: 145 -154.  Mikkola, H. 1981. Der Bartkauz. Neue Brehm-Bücherei 538, A. Ziemsen Verlag, Wittenberg- Lutherstadt.  Mikkola, H. 1992. Wood Owls, pp. 108-140. In Burton, J.A (Ed.) 1992. Owls of the World, Revised  Edition, Peter Lowe, London.  Stefansson, O. 2013. Lappugglan (Strix nebulosa lapponica) i Sverige. 63 pp. Boden.
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