Assessing different management scenarios to reverse the declining trend of a relict capercaillie population: A modelling approach within an adaptive management framework

Capercaillie populations are declining in most of its distribution area and are especially vulnerable in southern Europe. There, the causes of decline have not been properly identified and conservation decisions are too frequently based on poor evidence. We analysed the trend of a relict capercaillie population in the Spanish Pyrenees on the basis of bird densities during the period 1989–2010, and we developed the first modelling exercise for the dynamics of a capercaillie population in southern Europe. We also explored management actions commonly used to enhance endangered prey species thought to be affected by hyperpredation: the release of captive-bred females, in varying numbers, the removal of predators and the combination of both actions, using available information from past captive-breeding experiments and from an ongoing experiment involving the removal of terrestrial mesopredators. The population was found to be declining at an annual rate of 4%. Restraining the unknown adult survival rate according to values reported in the literature, our modelling approach showed that recruitment (productivity + fledgling survival), rather than adult survival, was the demographic parameter to be improved as a result of management and, thus, most likely to increase the population growth rate. The removal of terrestrial mesocarnivores may lead to the stabilisation of the capercaillie population (lambda 0.99 ± 0.06), through the improvement of productivity, although this result should be considered as preliminary. However, the most effective management strategy was the combination of predator removal together with the release of 15, 30 or 45 adult females per year. These strategies should be viewed as urgency measures and should be implemented in combination with other long-term measures, such as the reduction of forest density, which may influence predation rate and food availability, and the control of the numbers of wild ungulates, which could be subsidising mesopredators in the area. We also present the adaptive management framework which will allow the results obtained from our current modelling to be updated in the near future, what will reduce the uncertainty regarding the best conservation strategies to apply in this and other similar populations.