Effects of wind farms and food scarcity on a large scavenging bird species following an epidemic of bovine spongiform encephalopathy

Abstract

Summary 1.Wind farms are emerging as a major cause of mortality of large scavenging bird species, which may be catastrophic when they operate in concert with other threats. As a study model, we examine the impact of wind turbines on the population dynamics of a soaring bird species, when acting in conjunction with a sudden decrease in food availability following the European bovine spongiform encephalopathy (BSE) epidemic. 2. In Spain, vultures have been provided with supplementary food at traditional vulture restaurants for centuries. In 2006 ⁄ 2007, these feeding stations were closed as part of disease control measures. At the same time, wind farms were deployed within the vulture foraging range. We used capturerecapture data and direct observation to monitor the impacts of these changes on the vulture population. 3. The number of breeding pairs decreased by c. 24%, adult survival by 30% and fecundity by 35%. However, the population recovered as soon as the perturbations ceased, the vulture restaurants were reopened, and the most problematic wind turbines were closed. Population recovery was faster than predicted by a retrospective stochastic population model. 4. Our analyses indicate that fecundity and survival were influenced predominantly by wind turbines. Food scarcity promoted a shift in foraging behaviour that drove vultures to fly into the path of wind turbines as they sought out new food sources in a landfill site. Elasticity and sensitivity analyses of the population model showed that mortality of adult birds had a much greater effect on population declines than mortality of immature birds, whereas reduction in fecundity had negligible effects. 5. The most likely explanation for the rapid recovery of the vulture population is that the observed decline in breeding pairs was not solely because of increased mortality. The decline probably included dispersal away from the area and a greater incidence of skipped breeding during the perturbation years. Subsequent immigration from large nearby populations was probably a factor in population recovery. 6. Synthesis and applications. Where specific wind turbines are causing substantial mortality, their closure is an effective management response. For vulture populations dependent on supplemental feeding stations, the feeding sites should be relocated away from the most problematic wind turbines, or other anthropogenic sources of mortality, to prevent negative impacts. We recommend the establishment of scattered, low-value food sources to replicate historical conditions and to avoid the problems associated with high concentrations of individuals in one place.

Population control of an overabundant species achieved through consecutive anthropogenic perturbations

“…We present evidence of how these two consecutively occurring perturbations have been extremely effective in reducing the population density of a generalist opportunistic bird, which has not recovered in the three years following these events. Under strong perturbation pulses (Martı´nez-Abraı´n et al 2012) or intense environmental variability (Harding et al 2011), the density-dependent responses of demographic parameters appear insufficient to buffer population changes. Although an isolated perturbation, such as poisoning, seemed to have an important short-term effect, it is reasonable to believe that it was the closure of the landfill site that led to a permanent decrease in the carrying capacity of the system and hence a long-lasting reduction in population numbers, as previously suggested by Oro and Martı´nez-Abraı´n (2007).…”

Ranging Behaviour of Non-Breeding Eurasian Griffon VulturesGyps fulvus: A GPS-Telemetry Study

“…However, since the outbreak of the neurodegenerative disease in cattle, Bovine Spongiform Encephalopathy (BSE), mandatory regulations of the European Union led to the temporary closure of existing vulture restaurants in order to avoid the likely risk of transmission to humans (the Creutzfeldt-Jakob disease). Consequently, owing to this temporal food shortage, the populations of scavengers seem to have been affected, with survival and breeding success being reduced (CamiZa & Montelío 2006, Martínez-Abraín et al 2012.…”

“…However, little is known about ranging behaviour and spatial parameters. This is key to help managers to improve conservation measures aimed at combining the maintenance of scavengers' populations with sanitary legislation, as well as for the installation of wind-farms, which also constitute a potential source of mortality (Tellería 2009, Martínez-Abraín et al 2012. Traditional ringing schemes and radio-tracking studies have shown that the species ranges extensively, particularly juveniles (e.g.…”

“…The species is globally and regionally catalogued as "Least Concern" (Del Moral 2009, BirdLife International 2011. Habitat loss, rural abandonment, intensification of farming practices, and rising of non-natural mortality caused by poisoning (Gangoso et al 2009), pollutant ingestion (Hernández & Margalida 2008, Lemus et al 2008) and collision with wind-farms (Tellería 2009, Martínez-Abraín et al 2012, are the main threats to vulture populations (García-Ripollés & López-López 2011).…”

Canadian Estimate of Bird Mortality Due to Collisions and Direct Habitat Loss Associated with Wind Turbine Developments

“…The behavior of some diurnal migrating birds, such as raptors, makes them vulnerable to collisions with wind turbines, particularly if they are hunting (Higgins et al 2007, Garvin et al 2011, Martínez-Abraín et al 2012). Raptor mortality rates were particularly high at some early, large-scale wind energy facilities in California, e.g., Altamont (Orloff and Flannery 1992).…”