Effects of power lines on a White Stork Ciconia ciconia population in central Spain

The aims of this article are 1) to study the effect of mortality at power lines on a White Stork population and 2) to know which are the risky factors on both collision and electrocution incidents in a humanised area. Location: Study area was located at South-eastern Madrid (600 m a.s.l.), in Central Spain. Methods: The area was surveyed between early December 1999 and late November 2000 to estimate monthly population of Storks presents at the study area. Twelve different power line sections and 129 steel power poles were surveyed monthly to study mortality by collision and electrocution. To control for underestimated collisioned and electrocuted casualties we calculated correction index. Correlation analysis, chi-square test, principal components analysis and logistic regression were used to test that 1) the mortality at power lines was related with population size in the area; 2) there are differences among mortality by lines type and poles type; 3) mortality by collision was related with environmental variables around power lines; and 4) environmental parameters influences electrocution risk on pylons. Results: We found that ca. 1% present population during postbreeding migration died on powerlines and 7% population did during preebreeding migration and wintering season. Deaths were nearly anecdotal during breeding season. Collision with wires and electrocution on pylons were both associated with rubbish dumps selection as foraging habitat. Annual mortality rates of collision (3.9 birds/km) and electrocution (0.39 birds/pylon) were the highest rates never found in Spain. Mortality on power lines was a density-independent limiting factor of this White Stork population. Collisions with transmission lines were significatively higher than those with distribution lines, though our mortality rate in distribution lines was also higher than other regions.

Garrido, J. R. & Fernandez-Cruz, M., Ardeola 50(2), 2003, 191-200