Environmental Engineering Reference
In-Depth Information
Eagle nests at BPWF and SBWF are located in protected remnant vegetation that is
not subject to disturbance from human activities such as forestry or vehicular traffi c.
The wind turbine layout incorporated a buffer of at least 500 m between the turbines
and nests. This buffer has not been breached or compromised at these nests and there is
no, or extremely limited (i.e. with the exception of breeding success surveys), human
activity within the buffers. This contrasts with other eagle nests in Tasmania where
activity can occur outside the usual 10 ha reserve (which equates to a minimum dis-
tance of 180 m between the nest site and the activity during the breeding season).
It is interesting to note that the eagle nests at these wind farms have been used by
eagles consistently across the years of the study, even though it is widely documented
that eagles have alternative nests within their territories and do not always use the same
nests in consecutive years (Wiersma and Koch
2012
; Forest Practices Authority
2013
).
It does suggest that the nests on the wind farm are used more regularly than others
elsewhere, but the reasons for this cannot be determined from existing data.
Behavioural studies documented how eagles interact with turbines at these wind
farms. These included how eagle behaviour changed under specifi c operating and
environmental conditions at the wind farms (Hull and Muir
2013
). It quantifi ed tur-
bine avoidance rates, and is one of the few cases where avian avoidance rates have
been quantifi ed from observational studies. There is a general dearth of data on avoid-
ance rates, which is a constraint to predictive modelling, whose purpose is to estimate
the collision rate of species at a proposed wind farm (Chamberlain et al.
2006
; Masden
et al.
2009
; Garvin et al.
2011
). Behavioural studies showed that both WTE and
WBSE altered their avoidance rates according to the operational status of the turbines.
WTE also increased their avoidance rate under poor weather conditions. This suggests
that eagles respond to perceived changes in risk, which begs the question of why they
still occasionally collide with turbines (Hull and Muir
2013
).
Much has been learnt about how eagles respond to these wind farms. This
includes: quantifi cation of collision rates; that collisions at these sites were indepen-
dent and random in time; no measurable disturbance effects of the wind farms; and
changes in behaviour of eagles in response to turbines. There remains more to
understand, particularly: factors involved in eagle collision risk; whether the data
from these two wind farms are representative of other sites in Australia, and whether
the data are also representative of other species of raptor. A more thorough under-
standing of the factors involved in collision risk would potentially allow develop-
ment of specifi c management interventions to reduce collision risk. It is important
to reiterate that it is important to apply robust, scientifi c approaches to studies such
as these and they must include clearly defi ned, achievable objectives, robust survey
design and analysis, and evidence-based approaches. These are key to understand-
ing how eagles interact with wind farms, the extent of impact and the development
of effective management interventions. To use contrary approaches is inconsistent
with the precautionary principle (see Stein
1999
) .
Acknowledgements
The fi eld data was conducted predominantly by Wildspot Consulting for
which we thank them. We also thank Robert Barbour for his involvement in recent years. The vari-
ous owners of these wind farms have provided the necessary support for the scientifi c analysis of
the monitoring data. We thank two referees for their useful comments.
