Male capercaillie were censused at their leks in spring 2001 in most parts of their range in Switzerland. A large part in the canton of Grisons was not censused with the same method bud by a stratified sampling of tracks, droppings and feathers. The capercaillie is distributed in the Jura mountains, along the northern slopes of the Alps and in the central Alps of the canton of Girsons. On 147 leks, 252 Capercaillie were counted. The total number of Capercaillie males in Switzerland is estimated to be between 450 and 500. In 1968/1971 and in 1985 two censuses had been carried out with the same method. The first revealed an estimated number of Capercaillie males of at least 1100, the second 550-650. Since 1985, the range has shrunk, too. Capercaillie has almost completely disappeared from the northwestern slopes of the Alps. The main reasons for the long-term negative trend in population numbers of Capercaillie seem to be changes in forest structure and human disturbance. Meteorological data suggest that between 1985 and 2001 the decline has been overlayed by population fluctuation caused by changing weather conditions.