Raptor electrocution mortality on power lines has been well documented over the past several decades, yet knowledge gaps, particularly regarding electrocution rates and estimates of losses, are still prevalent in the literature. Mortality estimates that do exist are often derived solely from utility outage records and exclude those not associated with a sustained outage. To address these shortcomings, we directly assessed raptor electrocution mortality beneath distribution power lines in east-central Alberta, Canada between June and August 2003. We also experimentally tested the effect of scavenger removal of carcasses. We observed the greatest rate of raptor mortality on transformer poles; 3-phase corner deadend poles were implicated in more incidents than expected based on proportional frequency, whereas tangent structures showed the opposite result. An estimated 94% of electrocution mortality was not associated with a power outage, indicating that utility outage data alone is insufficient to estimate incidence of electrocution. Scavenger removal rates were high, with >50% of the experimental carcasses removed within 7 days. Study results will assist utility companies and wildlife managers to better delineate structure retrofitting and new construction standards for structures that cause a disproportionately high number of raptor electrocutions, maximizing limited mitigation funds. Ó

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