Spatial endangerment of capercaillie (Tetrao urogallus L.) populations in Slovenia in 1998

Miran Čas (1999) Spatial endangerment of capercaillie (Tetrao urogallus L.) populations in Slovenia in 1998. Zbornik gozdarstva in lesarstva (60). pp. 5-52. ISSN 0351-3114

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Abstract

In 1998, 473 hunters and foresters participated in a repeated pan-Slovenian survey of capercaillie (Tetrao urogallus L.) leks activities in 1.234 observations. Out of the total of 559 surveyed leks only 273 (49%) are still active. Out of 495 leks (88.6%) in the Alpine region 51% were established as active and of the other 64 leks in the Dinaric region 33%. Active populations are present in 74% of the surveyed distribution area. 83% of the distribution area have been preserved in the Alpine (0.22 birds/km2) and 19.7% in the Dinaric region (0.07 birds/km2) in 4 839 km2 or 22% of Slovenian area. The share of active leks in forests in 200 m- altitude zone areas increases linearly, from only 16% of active leks from 601 to 800 m above sea level to 70% from 1.401 to 1.600 m (timber line is at 1.650 m). Below 1.000 m there areonly 11.2% of all active leks. The optimum of population density was established from 1.201 to 1.600 m in 66% of all active leks, with 0.59 birds and 0.18 of active lek/km2. After 1986 the number of active leks has fallen by199 (42%), 41% of this in the Alpine and 53% in the Dinaric region. The number of deserted forest leks grows linearly with decreasing in 200 m - altitudinal zones, from 22,9% from 1.400 to 1.600 m to 78,9% from 601 to 800 m. Deserted or most endangered are the margin distribution regions in the sub-Alpine region and in the entire Dinaric region. The greatest number of sub-populations has been preserved in remote high-altitude Norway spruce and beech forests.

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