Capercaillie (Tetrao urogallus) is a grouse highly sensitive to human activities and declining throughout most of its European range. The Cantabrian subespecies Tetrao urogallus cantabricus is the most endangered and the only inhabiting caducifolious forests. Although many causes have been suggested as possible reasons for its alarming decline, no definite evidence supports any of them. Hence, the only effective measure so far is habitat conservation. In this sense, wind farms development is an emergent threat to this population. In a recently described Mediterranean habitat, we assessed Capercaillie occurrence before and after a wind farm construction in a wintering site. After construction Capercaillie presence signs decreased to zero and space use changed, likely due to human disturbances derived from the wind farm construction and maintenance. These changes in habitat use at a local scale and related negative effects on Capercaillie are discussed. As part of the precautionary principle conservation measures for this subespecies should avoid any wind farm within the current Cantabrian Capercaillie range while further research on Capercaillie and wind farms interactions should be urgently carried out.