To understand the effect of added mortality produced by wind farms on Black Harrier populations, we first defined a model for the population dynamics of the species, then we simulated population trajectories under different levels of additional mortality. We start by describing the current population number and trend for the species. In absence of annual population counts, we used SABAP2 presence-absence data \citep{Brooks2020} to estimate a Bayesian dynamic extension of a Royle-Nichols model \citep{Royle2003,Altwegg_2019,Rossman_2016}. Our data consists of a number of sites (i.e. pentads, representing 5' latitude and 5' longitude) that are sampled each year several times, recording presence or absence of the species of interest. The number sites and the number of visits to each site may change from year to year. In each year, we selected only those sites that were visited at least five times to have sufficient data to estimates the probability of detection with confidence.