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Wädenswil, Switzerland

Michael Gramiger,Zorcher Hochschule for Angewandte Wissenschaften WadenswilCH | Bitterlin L.,Wildtiermanagement WILMA | Graf R.F.,Wildtiermanagement WILMA
Schweizerische Zeitschrift fur Forstwesen | Year: 2015

Conservation measures to further the remaining capercaillie populations in Switzerland focus mainly on improving habitat quality of the forests. So far, programs to survey the effect of these forestry measures have been restricted to changes in forest structure and capercaillie presence on the treated areas. Potential changes in arthropod food availability, a key factor for the habitat quality for chicks in their first weeks of life, however, have not been assessed systematically in Central European habitats. We measured the biomass of arthropods in four habitat types: dense, semiopen and open stands and inner forest edges. In our study area in the Swiss Prealps, these habitat types resulted from logging activities in twelve cable-way lines between 2008 and 2011 that were carried out with the aim to improve habitat quality for capercaillie. Arthropod availability varied strongly between plots and high numbers of individuals could be observed in all four habitat types. Coleoptera accounted for more than half of the total dry weight of the catch. Summing up the three most important arthropod groups for the chick diet as reported in literature (spiders, ants and lepidoptera larvae), open stands, forest edges and semiopen stands yielded higher arthropod biomasses than the dense stands that had not been treated in the logging campaigns. In this case study, habitat improvement measures increased the arthropod food supply, and thus probably improved the conditions for capercaillie chicks in the first weeks of their development.

Hummel S.,Wildtiermanagement WILMA | Graf R.F.,Wildtiermanagement WILMA
Schweizerische Zeitschrift fur Forstwesen | Year: 2014

According to Scandinavian literature, Lepidoptera larvae are particularly important for the rearing of capercail-lie chicks. For Central European habitats, we lack detailed information on invertebrate food availability as a function of habitat conditions and season. Using the sweep-net sampling technique, we examined the phenology and spatial distribution of larvae in forest stands with bilberry vegetation in dependence of the canopy cover and the duration of sunshine. The availability of Lepidoptera larvae was highest in mid of June and decreased to almost zero in July. The abundance and biomass of Lepidoptera larvae was lower at sunny (sunshine duration 4-10 h) and open locations (canopy cover 0-30%) than at shady places (sunshine duration 0-3 h) with intermediate canopy cover (35-60%). These results lead to the conclusion that forests with an intermediate canopy cover provide better foraging habitat for capercaillie chicks than very open and sunny forest stands. Further, the timing of hatching and the phenology of Lepidoptera larvae may be an important issue in Central European habitats. However, in Switzerland we lack information on reproductive success to study this connection more profoundly.

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