Capercaillie populations in Switzerland declined significantly during the 20th century. The loss of suitable habitats is considered to be the main reason for this decline. For the Pre-Alpine region of the Schwägalp, aerial photographs and a statistic model were used to quantify changes in the availability and distribution of capercaillie habitat. We detected a loss of suitable habitats. However, this loss alone can not explain the extensive decline in the population of this endangered species.