engleski

Reconstructing reasons for unsatisfactory status of Western Capercaillie (Tetrao urogallus) in Croatia through time and space

Western Capercille (Tetrao urogallus) is bird species with wast distribution across western hemisphere but unsatisfactory conservation status in Croatia. During last century significant decline of population occured. Croatian Book of Birds of Croatia classified status of the national population as endangered. We tried to reconstruct main driving forces that caused population collaps in the last decades. We collected all available information on species from monitoring program such as: lek distribution on part of the distribution range, number of meles and femeles at leks, hunting practice, hunting period and similar. Knowing the species connectedness with spatial distribution of some plant species, we evaluated the Croatian territory for suitability of preferd species, Vaccinium mirtillus. In that proces, we used diverse spatial environment variables like land cover, climate variables, acidity (ph) of the soils as well as variables prepared by authors, like Shannon-Wienner Index of habitat diversity . Technique used was Ecological Niche Factor Analysis (ENFA), method that uses presence-only data to describe the marginality and specialisation factors of the species. Marginality describes species selectivnes of specific habitat characteristics in regards to available habiats in the area and specialisations reveals niche breath. The valorisation of Croatian territory for Vaccinium mirtillus revealed very good match with hystorical distribution of Western Caperceille in the country. Furthermore spatial evaluation reveiled habitat fragmentation as the most probable reason for creating smaller ”islands” of sub populations in the past that could not communicate ammong each other. This eventually led to local extinctions. Additionally, we evaluated hunting practices through time that disabled population to recover. In the light of our findings we evaluated new plans of hunting organisations for enlargement of game production in the area of remaining active laks in the country.

habitat suitability; landscape; population decline; habitats

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