Wind farms generate little or no pollution. However, one of their main adverse impacts is bird mortality through collisions with turbine rotors. Environmental impact assessment (EIA) studies have been based on observations of birds before the construction of wind farms. We analysed data from 53 EIAs in relation to the actual recorded bird mortalities at 20 fully installed wind farms to determine whether this method is accurate in predicting the risk of new wind farm installations. Bird data from EIAs were compared with bird collisions per turbine and year at functional post-constructed wind farms to identify any relationship between pre- and post-construction studies. Keywords: bird collision, environmental impact assessment, Falco sp., Gyps fulvus, mortality data, raptors, Tarifa, wind farm.