Lanz, M. & K. Bollmann
(* = Kurzbeitrag)
Eigenschaften der Schlaf-, Ruhe- und Äsungsbäume des Auerhuhns Tetrao urogallus im Waldreservat Amden.
(von 1994 bis 2006 vergeben)
Lebensraum, Habitatwahl, Waldstruktur, Baumstruktur, Deckungsgrad, Fluchtdistanz, Artenschutz
Schweiz, St. Gallen, Amden
Characteristics of individual trees selected by Western Capercaillie for roosting, resting and feeding – a study at a forest reserve in the Swiss Prealps. Trees are key factors in the winter habitat of Western Capercaillie Tetrao urogallus. They provide food, shelter and protection against predators. In winter, the species mainly feeds on conifer needles and spends most of the time in or below trees. By means of the number, distribution and characteristics of droppings on the snow surface, trees for roosting, resting and feeding can be distinguished. In our study in the Swiss Prealps, we investigated the distribution and characteristics of these types of «Capercaillie trees» in the forest reserve of Amden in winter 2006. We compared 75 pairs of trees selected by Capercaillie as night roost, for feeding or resting with 75 matched control trees by the use of a logistic regression and a set of predictor variables. They were specifically selected so as to describe individual trees, sites of trees, forest stands and edge elements. The latter included structural elements that provide protection for Capercaillie on the ground. The most important factors discriminating roosting, resting and feeding trees from random trees were tree species, number of forest aisles and openings together with canopy cover. Capercaillie strongly selected silver fir Abies alba and basal-branched Norway spruce Picea abies as feeding and resting trees, respectively. The ratio of forest stands with two and more aisles was significantly larger for Capercaillie trees compared to matched random trees. Roosting and feeding trees were characterised by a high density of branches in the upper third of the trees. Resting trees had a high number of edge elements and an intermediate number of forest aisles in the surrounding areas. Our results suggest that Capercaillie selectively choose individual trees to meet food requirements, predator avoidance and energy demands. An effective conservation of the local population has to include a forest management that considers (i) the protection of frequently used trees, (ii) basal-branched Norway spruce and old-growth silver fir as individual elements, and (iii) forest stands with an adequate number of forest aisles and openings and a sufficient amount of edge elements.
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