Search areas for monitoring bird and bat carcasses at wind farms using a Monte-Carlo model

Bat fatalities at two wind farms in Tasmania, Australia: bat characteristics, and spatial and temporal patterns

“…Observers searched beneath turbines in concentric circles on foot and using slowmoving 4WD motor bikes from the base of the turbine tower out to 100 m (consistent with Hull & Muir 2010). The concentric circles were 2Á10 m apart, with the wider spacing used during eagle searches (as eagle carcasses were more conspicuous and readily detected; Hydro Tasmania, unpubl.…”

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

“…The distribution of carcasses in relation to distance from the turbines is unlikely to vary much among sites, because it is affected mainly by the height of the turbines (Hull and Muir 2010), which is very similar for most Canadian turbines, and is not affected by habitat, searcher efficiency, or scavengers. Hull and Muir (2010) used a Monte-Carlo approach based on ballistics to model the proportion of carcasses that would be thrown various distances from a turbine, assuming that birds acquire a forward momentum based on the speed of the blade and are equally likely to be hit anywhere along the length of the blade.…”

“…Most of the difference in Smallwood's estimates, compared to ours, appears to be due to differences in the correction factors rather than a difference in the number of carcasses found in the data he analyzed. For example, he used larger corrections for birds falling outside a 50 m radius; by assuming a logistic distribution of carcasses, he concluded that carcasses could fall up to 156 m away from an 80 m turbine, though this is farther than Hull and Muir (2010) suggested is likely. Furthermore, his analysis assumes that mortality is proportional to the rated capacity of the turbines, but particularly for newer turbines this seems unlikely; for example, there is only a 19% increase in the blade swept area between a 1.5 and 3.0 MW turbine (http://site.geenergy.com/prod_serv/products/wind_turbines/en/15mw/specs.…”

“…This may lead to an overestimate because, on average, one would expect carcasses to be exposed to potential scavengers for only half the search period, e.g., for a typical three-day search interval, birds would be equally likely to be killed one, two, or three days before the search, leading to an average exposure of 1.5 days. Our correction factors may also be biased low if some birds fall beyond 85 m (Jain et al 2007, 2009, Smallwood 2013, although ballistic modeling suggests very few birds are expected beyond that distance (Hull and Muir 2010). On the other hand, we assumed that all birds found during carcass searches died as a result of colliding with the turbines.…”

Avian collisions at two wind farms in Tasmania, Australia: taxonomic and ecological characteristics of colliders versus non-colliders

“…Observers searched beneath turbines in concentric circles on foot and using slow-moving 4-wd (quad) bikes from the base of the turbine tower usually out to 100 m (consistent with Hull & Muir 2010). The subset of turbines surveyed for all species were surrounded with predator-proof fences to minimise removal by mammalian scavengers and pasture was maintained at a low height to increase visibility.…”