Wind Farms and Biodiversity: Improving Environmental Risk Assessments - Wind and Wildlife - page 45

Collision Risk Assessment
Turbine design and operational parameters were provided by the developer (sourced
from the manufacturer), while parameters relating to falcon morphology were
obtained from Marchant and Higgins ( 1993 ). Daily collision rates were estimated
by calculating the proportion of time each falcon spent fl ying at RSA within a 200 m
buffer (i.e. as a conservative measure describing a potential to interact with a turbine)
of a turbine followed by modelling using the Band Less Predictable Flights Model
(Band et al. 2007 ) implemented in the Monte Carlo simulation software GoldSim V
10.5 ( 2010 , www.goldsim.com ) and the result for each day averaged across the
number of sample days.
Avoidance Rate
Although avoidance rates have been estimated for several species of bird of prey
(see Whitfi eld and Madders 2006 ; Hull and Muir 2013 ), the rate at which New
Zealand falcons might avoid turbines is currently unknown. Empirically derived
avoidance rates for a range of bird of prey species are consistently high, with values
typically falling between 98 and 100 % (Whitfi eld and Madders 2006 ). In this study,
avoidance was modelled using values reported in Whitfi eld and Madders ( 2006 ) for
the related, and behaviourally similar, prairie falcon (i.e. between 99.5 and 100 %).
Because this range is based on just two studies and in the absence of established
avoidance rates for New Zealand falcon, we adopted a conservative approach by
using the lower value of that range in the models (i.e. 99.5 %).
Results
During autumn, with the exception of March, the adult male's home range was
about twice the size of the adult female's home range for all three kernel contour
levels analysed (Table 1 ). The male's 95 % kernel home range increased from a
March low of 105 ha to a May peak of 2,966 ha before decreasing to 661 ha and
425 ha for June and July, respectively. The mean (±1 standard error) 95 % kernel for
the male across all months was 1,030 ha (±505 ha). In contrast, on a monthly basis
the adult female's 95 % kernel home range declined from a peak in March of 660 ha
to stabilise between 226 ha and 310 ha, respectively, for the remaining months
(Table 1 ). The degree of overlap in home range between the sexes was approxi-
mately 50 % at all kernel levels, indicating that adult male and female falcons did
not hold exclusive home ranges.