MJBS 14(1-2).indd

The Oyu Tolgoi (OT) project, one of the world’s largest copper and gold mines, is located in Gobi Desert of Mongolia. To help meet its target of Net Positive Impact on key biodiversity features such as the Houbara bustard (Chlamydotis undulata) the OT installed bird fl ight diverters (BFDs include spiral and fl apper devices) to its power transmission lines to reduce the risk of birds hitting the wires. Despite the many studies demonstrating that BFDs reduce collision rates, we could fi nd no published information on malfunction rates of BFDs. In January 2013, we surveyed the physical function of 1,200 BFDs (e.g. 600 fl appers and 600 spirals) in three sample areas on each of four lines of varying voltage and structure. Of the 600 fl appers examined, 123 had malfunctioned within nine months of installation, while the malfunction rate of the 600 spirals studied was zero. Using a Generalized Linear Mixed Model, we found that the rate of fl apper malfunction increased with decreasing fl apper size and power line diameter. Further, the fl apper malfunction rate increased as the distance between poles increased. The cost of replacing malfunctioning BFDs is very high as there are serious health and safety constraints related to working with live wires. Factors aff ecting diverter malfunctioning need to be considered for future powerline projects and our information can serve as basis for developing national standards or regulations for powerline mitigation in