Space–time trends in Spanish bird electrocution rates from alternative information sources

Interaction with man-made infrastructures is one of the main sources of non-natural bird mortality. Here, we use a long-term study (1980–2010) to analyse spatial and temporal patterns in avian electrocution in Spain, using ringed birds as well as published reports and articles as information sources. Electrocution rates of ringed birds differ from rates obtained in unringed species. Electrocution rates are likely seasonally asymmetrical and are not constant across study periods: between 1990 and 2005 an annual rising trend of 5% was observed, whereas between 2006 and 2010 this trend decreased (16% annually). From the literature, we confirmed this decreasing trend. However, when we consider large eagles (Aquila genus), which include several of the most threatened bird species in Spain, this decreasing trend is not evident. The results of the analysis of different environmental and socio-economic factors affecting bird electrocution rates are similar between ringed birds and traditional power line surveys. Our modelling suggests three common factors that influence mortality rates: number of hunted rabbits, tree coverage and length of the power line network. Thus, the use of alternative information sources to detect high mortality areas due to electrocution by power lines may be a useful tool to complement other methods.