"Many of our bird species are prone to colliding with overhead power lines whilst in mid flight" says Jon Smallie, Manager of the EWT's Wildlife and Energy Interaction Group (EWT-WEIG), which incorporates a long-standing strategic partnership with Eskom.
"To solve this problem, conservationists and electrical utilities around the world have, over the last 30 years, developed various marking devices that aim to make power lines more visible to the birds.
These devices have largely been developed based on what we think birds can see, but bird vision is fundamentally different from human vision. We hope that with a better understanding of how birds see their surroundings, we will be able to design improved marking devices and ultimately save more birds."
Preliminary findings show that bird families differ in their ability to see, and that several of the relevant species have far better peripheral than frontal vision. This has major implications for collision with power lines that are invariably in front of birds in flight.
Drawing a bird's attention to the front, in order to see an overhead power line, may be even more important than previously thought. The final results of the study will be ready by early 2010 and will be published on the EWT's website at www.ewt.org.za. The EWT intends to incorporate this new knowledge into the design of marking devices as soon as possible through its strategic partnership with Eskom.
Graham Martin – Professor of Avian Sensory Science at the University of Birmingham - is an international expert in bird vision. Professor Martin has developed a method for measuring bird visual fields (where they see) and acuity (how well they see) and is instrumental in this project, leading the research that will help the EWT understand how large birds, which are particularly prone to flying into power lines, experience the world while in flight.
Professor Martin recently spent two weeks in South Africa, measuring visual fields on blue cranes (Anthropoides paradiseus), white storks (Ciconia ciconia) and kori bustards (Ardeotis kori), all species that are frequently killed as a result of flying into power lines.
This is the first time that research of this nature has been undertaken with regard to bird power line collisions. Data were collected using captive birds at two participating institutions. Tygerberg Zoo in Cape Town and the Johannesburg Zoo provided four blue cranes and two white storks and a kori bustard respectively.
Various different power line marking devices are currently available, but all are installed five to 10 metres apart along power lines that are considered to be of collision risk to birds. While these devices have been effective in reducing the number of collisions, they do not completely eliminate deaths and effectiveness varies between bird families.
The EWT-WEIG is working with Eskom to improve their effectiveness. The Eskom-EWT Strategic Partnership started 13 years ago in response to problems such as bird collision and is a world leader in addressing this major unnatural cause of death in large birds.
This research is funded by Eskom and was undertaken in collaboration with Professor Graham Martin of Birmingham University, and University of Cape Town Phd student Jessica Shaw. The Tygerberg and Johannesburg Zoos provided captive birds, and expert bird handling expertise.
photo: Lynette Strauss