Crows' nests on power poles : finding a solution

Abstract

Crows (Corvus cornix and C. corone) nest on power-poles throughout northern Scotland causing interruptions to electricity that cost the electricity provider more than £250,000 annually. I aimed to establish what factors influence the nest site selection of crows in the islands of Orkney to help determine ways to reduce pole nesting by these birds. Crows preferred nest sites in trees that were coniferous, tall, mature, densely grouped, and far from occupied houses. However, when such trees were scarce, the number of occupied houses was high, and there were no cliffs within 1km, crows were more likely to nest on power-poles. I found that the fitting of a Firefly diverter at sites where nests were removed was ineffective at deterring rebuilding, but rebuilding was less likely to occur the later in the season that nests were removed. Nests in the middle phase of construction were the most likely to be rebuilt. Making an appropriate decision as to when to remove a crow nest, therefore, would seem more effective for deterring nest rebuilding than is the fitting of Firefly diverters. Nest removal also reduced the level of pole nesting both within years and between years. Furthermore, planned interruptions led to fewer customers losing power and to a twelve-fold reduction in the number of minutes that customers were without power, relative to unplanned power-cuts caused by nests. I also attempted to determine the efficacy of providing alternative nesting platforms and of insulating the live wires on transformer boxes, but I collected too few data to confirm if either of these might reduce the number of power-cuts caused by crows' nests. As both nest platforms and insulation remain in place, however, data collected from these sites in the future may allow confirmation (or not) as to their value.