In this month’s research update we summarise research articles on wind farm impacts on migratory birds; a state-of-the-art detection system for reducing bird collisions with wind turbines; the first record of a tracked Egyptian vulture being hunted and traded in West Africa; and the potential negative impacts for scavengers as apex predator populations recover.     

Impact of wind farms on soaring bird populations at a migratory bottleneck. Martin et al. 2018. European Journal of Wildlife Research

The authors of this study examined monthly migratory soaring bird abundance in relation to long-term mortality rates at 21 wind farms located near the Strait of Gibraltar – the most important migratory bottleneck in Western Europe and also an important region for wind energy generation in Spain. A previous study by some of the same authors revealed that the collision rate of birds with wind turbines in this region was among the highest ever recorded for raptors, with griffon vultures being the most frequently killed species.  

Although monthly bird abundance was not directly related to the number of fatalities over the year, mortality rates peaked in the late summer and early autumn, coinciding with the peak autumn migration period. Griffon vultures were the most commonly killed species, with 416 recorded fatalities in the 9-year study period. A second mortality peak occurred in the breeding season, when a higher proportion of adult birds were killed. 

The authors suggest that the number of fatalities during autumn migration constitute only a small proportion (1%) of the total migrating population, and that most of the deaths are of juveniles; but that fatalities during the breeding season represent a substantial proportion (6%) of the local breeding population, with population-level impacts being likely at the local scale. [It is worth noting that the wind farms closest to the Strait, where mortalities of migrants might be expected to be higher, were not included in the analysis – Fig. 1 below]

Vultures are particularly susceptible to collisions with wind turbines due to their large size, limited manoeuvrability and tendency for wind farms to be located where they occur in high densities (often due to favourable topography and wind currents).  It is therefore essential that new methods for reducing bird collisions at wind farms are developed, as discussed in the next article.