2010

In recent decades, several studies have shown that overhead high-voltage power lines can cause significant bird mortality. It is estimated that 800,000 to 1 million birds die annually in the Netherlands due to collision with a high-voltage line (Heijnis 1976; Renssen 1977; Koops 1987). These include both resident and migratory birds (Heijnis 1976). The collisions are caused by birds seeing the lines too late or not at all, or failing to properly estimate the distance to the line (Osieck & de Miranda 1972; Koops 1987; Martin & Shaw 2010). Consequently, most collisions take place at the times when the high-voltage line is least visible. This is the case at night and dusk, but also in weather conditions such as fog or drizzle (Heijnis 1976; Renssen 1977; Hoerschelmann et al. 1988). Because the lightning wire is thinner than the phase wires and is not bundled with other wires, this wire is the least visible so most collisions occur with it (Hoerschelmann et al. 1988; Alonso et al. 1994). Because the number of birds dying annually from collision with a high-voltage power line is relatively large, relative to other causes of non-natural mortality, suitable methods of mitigation are sought. One commonly used method is marking the lightning wire to increase its visibility (Koops 1987; Janss 2000).

In the context of the Environmental Impact Assessment (EIA) for the new Randstad 380 kV high-voltage line between Wateringen and Beverwijk, research into wire casualties under the existing 150 kV high-voltage line near Hazerswoude was conducted in the winter of 2007/2008 by Bureau Waardenburg on behalf of the national grid operator TenneT TSO (TenneT). Specific research was conducted on the effects of different alternatives for the placement of the Randstad 380 kV high-voltage line on the Natura 2000 area De Wilck, which is of international importance as a wintering area for the lesser swan (Cygnus Bewickii) and the wigeon (Anas penelope).

As a follow-up to the above study, TenneT, in consultation with Bureau Waardenburg, decided to start a trial with a new type of wire markers in the same area. The aim is to test the effectiveness of these markings in reducing the number of cable casualties. The present report presents the results of this study and the resulting recommendations.