2001

The Bonelli's Eagle (Hieraaetus fasriatus) population decline in Europe has mainly been attributed to high levels of anthropogenic mortality. We evaluated the potential negative effects of collisions with transmission lines on a breeding population of Bonelli's Eagles in Catalonia, Spain. Between 1990-97, two of the 12 recorded deaths of breeding Bonelli's Eagles were caused by collisions with transmission lines. All transmission lines within a 5-km radius of 47 eagle nests were classified into two collision risk categories (low or high), depending on their locations and habitats. Pairs having high risk lines within 1 km of nesting territories had turnover rates twice as high as pairs with no such lines (0.16 ± 0.11 [±SD] vs. 0.08 ± 0.10). Greatest turnover rates were observed when high-risk lines occurred within 100 m of nesting territories. Our results suggest that transmission lines near Bonelli's Eagle nesting territories constitute a risk for eagles due to the danger of collisions. New transmission lines should avoid crossing areas near nesting territories and, as a precaution, those that are <1 km from eagle nests should be marked in some way.