Protecting birds from dangers posed by power lines and pylons
Electrocution and collisions with power lines are leading causes of death for many species of bird. Now Spanish scientists are shedding new light on the factors that contribute to these deaths. Their findings demonstrate that applying fairly simple measures in key locations could dramatically reduce the numbers of birds that die in these ways. The research has important implications for those involved in the conservation of endangered bird species. Every year, thousands of birds worldwide die when they are electrocuted on pylons and power lines. Electrocution occurs when the bird comes into contact with two wires or when it perches on a conductive pylon (e.g. one made of metal) and touches a wire at the same time. In Europe, birds such as raptors, storks, owls and corvids are all affected. Electrocutions pose a particular threat to some endangered species such as the Spanish imperial eagle (Aquila adalberti) and Bonelli's eagle (Aquila fasciata). Although at first glance pylons may look very similar to one another, there are in fact hundreds of different pylon designs and the risk posed by a pylon depends on both the design and its location. Furthermore, although measures to reduce the risk posed by pylons have been developed, their effectiveness has not been assessed. Scientists at Spain's University of Barcelona have been studying the issue of electrocution for over a decade. Writing in the Journal of Wildlife Management, they explain how they assessed the electrocution risk posed by almost 4,000 pylons in the region around Barcelona. They found that fewer than 10% of pylons account for over 50% of bird deaths. On the design front, the safest pylons are unearthed pylons with suspended pin insulators, alternate cross-arm configurations, and no connector wires. Location is also important; pylons that dominate the landscape, especially those placed in scrubland, are particularly deadly. This is because birds of prey often use them as perches to scan the surrounding landscape for prey. Crucially, the study also demonstrated that power companies do not need to apply corrective measures to all their pylons to reduce mortality from electrocution. Instead, applying mitigation measures to 'only 6% of the most dangerous pylons could reduce bird mortality by up to 70%', according to Joan Real, one of the authors of the paper. The researchers conclude: 'Our results indicate that electrocution of birds in a given area can almost be eliminated by means of a combination of an adequate pylon selection strategy with well-tested correction techniques, resulting in an optimal allocation of resources by public agencies and power line companies to bird conservation.' In a second study, published in the journal Bird Conservation International, the researchers address the issue of collisions. 'Collision with power lines is a lesser-known problem than electrocution and is harder to detect because it can occur at any point along the transmission line,' explains Professor Real. The greatest risk is posed by the earth wire, which is less visible. The researchers used radio trackers to follow the fate of 18 Bonelli's eagles; collision with power lines is the third greatest cause of death for this endangered species. 'The most dangerous spans for Bonelli's eagle collision are those situated in the areas more frequently used by eagles, that is, breeding and roosting areas (cliffs) and open hunting habitats (scrubland, farmland and grassland) far away from the human disturbance of urban areas, and along the flight lanes between foraging and breeding or roosting areas,' the researchers write. Implementing measures such as wire marking along these stretches could reduce the number of collisions, the researchers suggest.
Countries
Spain