Abundance and distribution of the Great Grey Shrike Lanius excubitor at Ljubljansko barje (Central Slovenia) in winters 2008/09, 2011/12 and 2012/13

Abstract

Results of the survey of wintering Great Grey Shrikes Lanius excubitor at Ljubljansko barje in winters 2008/09, 2011/12 and 2012/13 are presented. The census was conducted by 30-60 volunteers of the Ljubljana branch of DOPPS - BirdLife Slovenia. The survey area was divided into 13-20 census plots. Locations of Great Grey Shrikes, types of structures on which the shrikes perched, and heights of their perches were recorded. The numbers of wintering Great Grey Shrikes at Ljubljansko barje were estimated at 57 (2008/09), 51 (2011/12) and 67 (2012/13) individuals. Crude densities in the census area were 4.2, 3.7 and 4.9 individuals/10 km2, whereas maximal local densities reached 15.0, 14.6 and 14.8 individuals/10 km2. The analysis of the actual land use revealed higher densities of Great Grey Shrikes in the areas with a higher proportion of grassland and a lower proportion of arable fields and gardens in winter 2008/09; there was no such gradient in the other two winters. Great Grey Shrikes were most often observed in treetops, on powerlines and bushes in winters 2011/12 and 2012/13, while in winter 2008/09 they were more often observed on herbaceous stems and less often on powerlines. Moreover, the heights of their perches were lower than in the other two winters.