MITIGATION OF BIRD COLLISIONS WITH TRANSMISSION-LINES THROUGH GROUNDWIRE MARKING

A study was conducted to evaluate the effectiveness of groundwire mark ing in reducing bird mortality through collision at a power transmissi on line in southwestern Spain. Monthly Fight intensity observations an d weekly searches for dead birds were carried out at foul sectors of t he line comprising 28.2 km, during two consecutive winters, 1989-90 an d 1990-91, respectively before and after groundwire marking with colou red PVC spirals. Flight intensity and collision frequency decreased re spectively by 61% and 60% at marked spans compared to the same spans p rior to marking, while there was no significant change in collision fr equency at spans left unmarked After marking, the percentage of birds flying between the cables decreased and that flying above them increas ed Our results suggest that many birds avoided flying across the marke d spans of the line or climbed while approaching them, and therefore c ollided less frequently. The percentage decrease in mortality observed in our study falls within the range of results of other groundwire ma rking of removal studies.