Environmental Engineering Reference
In-Depth Information
(2009and2010,respectively)inanorth-southorientation(notethatthecurrentDSE
guidelinesrecommendtransectsinaneast-westorientation:DSE
2012
). Transects
werelateruploadedtotheplane'sGPSsystemforguidanceonceintheair.
Duringeachsurveytheplanelewatapproximately150-200maboveground,
following the pre-determined transect layout at a speed of 60-70 kt. Two observers
(one on either side of the aircraft) used binoculars to search all wetlands and sur-
rounding areas for brolgas within 250-500 m on either side of the plane. Records of
brolgas, brolga nests and unconfirmed brolga sightings (including nesting sites)
weremarkedonhandheldGPS(GarmineTrex)andaerialphotographsofnestsites
were taken to facilitate further investigation and ground-truthing. While the aerial
surveys were undertaken prior to the release of the recommended aerial survey
methodologyforbrolgas(DSE
2012
), it was broadly consistent with that method.
This survey technique (using the same methods as described here although with
east-west rather than north-south transects) has also been successfully undertaken to
locate brolga nests in other areas throughout south-west Victorian as part of the
assessments of other proposed wind farms (Biosis Research
2011
).
Ground Surveys/Truthing
Ground-truthing was undertaken to confirm the status of each nest identified during
the aerial surveys. This involved scanning wetlands from roads and tracks on private
property to confirm the existence of a nest at each record site and to attribute that
nest to a species. Brolga and black swan nests are of similar size (brolgas up to
142 cm, swans up to 150 cm diameter), and are raised mounds formed of grass,
sedges and other vegetation (Marchant and Higgins
1990
,
1993
), so attribution of
nests to either species was feasible only when adult birds were present on or near the
nest. While black swan nests tend to be darker than brolga nests (authors'
pers.
obs.
), there are records of brolgas using old black swan nests (Marchant and Higgins
1993
), which may confound any species attribution of nests without sighting birds.
We attempted to broadly compare the relative effort of ground and aerial surveys
to detect brolga nests. The effort (in man-hours) for aerial surveys was taken from
our flights undertaken in 2009 and 2010, while ground-truthing effort was taken
from our on-ground surveys in 2012/2013. The spatial areas covered in the 2 years
were similar, hence the values obtained were directly compared.
Number and Timing of Aerial Surveys
We then attempted to evaluate the use of a single aerial survey for detecting brolga
nests. Aerial surveys have only recently been recommended for brolgas in relation
towindfarms(DSE
2012
), and more information is helpful to refine the effective-
nessandsuitabilityofthetechniqueacrossdifferentareas.Foraerialsurveystobe
