Environmental Engineering Reference
In-Depth Information
Thesurveyresultsincludeatotalof127individualsof24speciesofbirdsand
four species of bats found to have been killed in collisions with turbines. Many
records are from a collection of feathers rather than a whole carcass and for this
reason some records could not be identified to species level. These include sulphur-
crested cockatoo and corellas (
Cacatua
spp.) and ravens (
Corvus
spp.). These data
are from a diversity of locations and the total numbers of bird and bat species that
mayoccuratthemwasnotprovidedtome.However,itissafetosaythatthe24
species recorded as collision victims represent a small proportion of the total of spe-
cies that occur at any of those sites.
Studies of birds at two wind farms in northern Tasmania (Hull et al.
2013b
)
reportedthat21%ofallspeciesrecordedatBluffPointWindFarmand18%ofall
speciesrecordedatStudlandBayWindFarmweredetectedinturbinecollisions.At
the same sites two of four species of microchiropteran bats present were detected
(Hull and Cawthen
2013
).
Which Species Are at Risk?
The discussion here is limited to the information available for the relatively small
number of wind farms mentioned above and results from my survey are qualified by
all of the limitations outlined above.
In the data collated for mainland sites, Australian magpies
Cracticus tibicen
account for almost one quarter of all detected fatalities and slightly more than one
quarter were comprised of two small raptors (nankeen kestrel
Falco cenchroides
and brown falcon
Falco berigora
). Three species (white-striped freetail bat
Nyctinomus australis
, swamp harrier
Circus approximans
and wedge-tailed eagle)
eachrepresentedbetween6and8%ofthetotaldetecteddeaths.Eachoftheother
species represented 1-2 % of all fatalities and 16 of these were represented by a
singleindividual.Itisassumedthat6%forthecombinedgroup'ravenspecies'is
likely to be comprised of up to three
Corvus
species.
It is evident that many species that are present at wind farms are not involved in
collisions. Simple presence at a wind farm and even frequency of flights of given
species do not appear to be useful predictors of collision risk. The poor correlation
between use of a site and collision risk has been discussed for raptors overseas
(Madders and Whitfield
2006
). It has also been shown for Tasmania (Hull et al.
2013b
) as discussed above.
The following general points are clear:
• The majority of collisions involved a small number of taxa;
• A disparate variety of taxa may collide with turbines; and
• The incidence of collisions is very low for the majority of species.
Information from studies at wind farm sites and from fatality data at operational
facilities gives some insights into reasons why collision risk varies between species.
Bird utilisation studies by Biosis that have documented flight heights for all bird
