Outdoor activities may have serious consequences for wildlife species that are sensitive to human disturbance. The pressure of outdoor activities on natural landscapes has increased dramatically in recent decades. However, we generally lack information on the spatial and temporal patterns of outdoor activities – a fact that makes it difficult to quantify the impact on wildlife and thus to implement and justify measures to constrain outdoor activities. In the winter seasons 2008 / 2009 and 2009 / 2010, we equipped 303 recreationists in the Val Müstair Biosphere Reserve, eastern Swiss Alps, with GPS loggers to record their spatial and temporal pattern of landscape use. We then analysed how the resulting pattern of spatial use overlapped with the habitat of capercaillie Tetrao urogallus, an endangered woodland grouse species that is highly sensitive to disturbance. For our study we used the official capercaillie core winter habitats observed by the game wardens of the Canton Grisons. The recorded 319 trips of 188 backcountry skiers and snowboarders and 231 trips of 115 snowshoers combined show an inhomogeneous use of subareas in the region. With one exception, the trips are located in the main valley and the adjoining southern and northern slopes and peaks. The trips of snowshoers result in a dispersed use pattern across the main valley, while the trips of the backcountry skiers and snowboarders are concentrated more on official and popular routes. Rarely did recreationists trespass official wildlife sanctuaries or cross capercaillie habitat patches. However, one official, very popular backcountry skiing route crosses one of the largest capercaillie habitats. Here the recorded trips show wide-ranging spatial use with many connectors to the main route. As a consequence, this capercaillie habitat patch is dissected into smaller undisturbed patches. GPS logging in combination with camera trap data provides detailed information on the spatio-temporal land-use pattern of outdoor activities. Based on these data, we identified a conflict of interest in the Val Müstair Biosphere Reserve that has to be resolved by management in a joint participatory process with the main stakeholders. Our methods and results could be transferred to other Alpine regions and be used for any land cover types. In this way we hope to contribute to mitigating conflicts between human outdoor activities and wildlife populations.