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Marti, C., A. Bossert & H. R. Pauli

Bestand und Verbreitung von Birkhuhn Tetrao tetrix und Alpenschneehuhn Lagopus muta im Aletschgebiet von 1970 bis 2015.

2016

113

1–30

Key words
(von 1994 bis 2006 vergeben)

Bestandserfassung, Bestandsentwicklung, Dichte, Bruterfolg, Balzbeginn, Balzplatz, Geschlechterverhältnis, Sommerwetter, Klimaerwärmung, Waldentwicklung, Waldgrenze, Gämse, Rothirsch, Prädation, Störungen

Schlagwort_Vogelart
(wissenschaftlich)

Tetrao tetrix, Lagopus muta

Schlagwort_Vogelart
(deutsch)

Birkhuhn, Alpenschneehuhn

Aletschwald, Riederalp, Aletsch-Bietschhorn, Kanton Wallis

deutsch

Abhandlung

Population trend of Black Grouse Tetrao tetrix and Rock Ptarmigan Lagopus muta in the Aletsch region (central Alps, Switzerland) from 1970 to 2015. – In the Aletsch region (canton of Valais, Switzerland), Black Grouse cocks are counted on their leks in spring, and Rock Ptarmigan in their territories, normally during at least two morning activity periods. The spring number of Black Grouse cocks in a study area of 5 km2 has fluctuated since 1970 without showing a trend, with a minimum of 13 cocks in the years 1998 and 2000 and a maximum of 38 cocks in 1990 and 1993. The number of Rock Ptarmigan in an adjacent part has increased from 17 cocks at the beginning of our censuses in 1974 to a maximum of 33 cocks in 1983 and 1984; then it decreased to a single cock in 2006. Since then, the population has increased again to 7–10 cocks. The area occupied by Ptarmigan decreased from about 4 to 2 km2. The decrease of Rock Ptarmigan numbers may have partly been influenced by climate warming. In a large part of the study area the abandonment of territories was caused by the growth of Arolla pines Pinus cembra and other trees. The Black Grouse leks moved during the study. The most important lek moved uphill by 120 m reaching a mountain ridge at 2210 m a.s.l. above the tree line. As in Ptarmigan, the changes are caused by the vegetation growing higher and denser. Our results show the importance of long-term monitoring programmes.