Environmental Engineering Reference
In-Depth Information
tic nest site when viewed from the air (Fig.
3
). As nests were not ground-truthed
immediately following aerial surveys, the two additional nests detected during
ground-truthing may have been built after the aerial surveys. Other crane aerial sur-
veys have also assumed 100 % detectability, either implicitly or explicitly (e.g.
Dreweinetal.
1996
;McCann
2001
; Motsumi et al.
2007
; Qian et al.
2012
).
When brolga nests were monitored throughout the breeding seasons of
2009/2010 and 2012/2013, availability varied between 10 and 90 % during a single
aerial survey. In this case, we would expect to detect new nests (i.e. built following
aerial surveys) while undertaking ground-based work in these areas, and this was
the case.
Conclusions
Consideration must be given to the objectives of a project when deciding if
aerial surveys are appropriate. We found that aerial surveys were a time-effec-
tive survey method for locating brolga nests when compared with ground
searches alone, even if the same area could be adequately searched from the
ground. Potential misidentification of nests means that ground-truthing is
required to confirm the identity of nests seen from the air, even if no follow-up
work is planned for those nests. The requirement to ground-truth aerial survey
results means that the two methods should be considered complementary when
searching for brolga nest sites. Variation in nest initiation dates by individual
brolga pairs over the season means that a single aerial survey is unlikely to
recordallthenestsforaseason,evenifdetectionis100%duringthelight.
Based on the 2 years of nesting data we present, two aerial surveys should
be undertaken to detect brolga nests: one a month after the first nesting obser-
vationfortheseasonandasecondamonthafterthat.Forthe2yearswhere
we have presented data, this method would detect approximately 75 % of the
knownnestsfortheseason(Fig.
4
). Subsequent ground-truthing and observa-
tional activities may detect additional nests initiated later in the season, or a
third aerial survey could be used approximately 6 weeks after the second.
Acknowledgements
We would like to thank the landholders who provided access to their proper-
ties to ground-truth aerial nest observations, Richard Hill (Department of Environment and
PrimaryIndustries)andInkaVeltheim(UniversityofBallarat)forreiningtheaerialsurveymeth-
odology and for their accounts on differentiating between brolga and black swan nests. An anony-
mous reviewer provided valuable comments to improve the content. Monique Elsley (Ecology and
HeritagePartnersPtyLtd)producedFig.
2
.
References
Arnol, J., D. White, and I. Hastings. 1984.
Management of the Brolga (Grus rubicunda) in
Victoria
-Technicalreportseriesno.5.EastMelbourne:DepartmentofConservation,Forests
and Lands.
