Bossert, A. & R. Isler
(* = Kurzbeitrag)
Bestandsüberwachung von Birkhuhn Tetrao tetrix und Alpenschneehuhn Lagopus muta in ausgewählten Gebieten der Schweizer Alpen 1995–2017
(von 1994 bis 2006 vergeben)
Bestandsentwicklung, Bestandsgrösse, Monitoring, Trend, Verbreitung
Tetrao tetrix, Lagopus muta
Monitoring of Black Grouse Tetrao tetrix and Rock Ptarmigan Lagopus muta in selected sites of the Swiss Alps 1995–2017. In the Swiss Alps, Black Grouse are counted in approximately 80 selected and exactly delimited sites, Rock Ptarmigan in about 50 sites since 1995. The number of cocks only is taken into account. Black Grouse cocks are counted on the leks. Male Rock Ptarmigan can be heard calling at the onset of activity, and they show display flights to mark their territories. As only sites where the respective species was present at the beginning of the censuses were included in the survey sample, only limited conclusions can be drawn about the total Swiss population. However, long term trends are detected.
After a decline in the mid-1990s, Black Grouse numbers recovered in most study sites and are more or less stable, though showing considerable annual fluctuations. On average, there are 3.6 displaying cocks per lek. The largest numbers of cocks on one lek were 8–18. Black Grouse seem to be able to adapt to small-scale habitat changes.
Numbers of Rock Ptarmigan have decreased by 13 % on average over all selected study sites since the beginning of the surveys. In the study sites in central Switzerland and in the cantons of Valais, St. Gallen and Grisons, numbers have stabilized at a lower level. In Ticino, numbers are only slightly lower than at the beginning of the counts. Of the seven study sites in Western Switzerland, three have not been occupied for several years. In 2016, the population density over all 43 counted study sites was 3–5 cocks per km2. Among the various investigated environmental factors, only an above-average temperature in July showed a clear correlation with the decline in Rock Ptarmigan populations.
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