Environmental Engineering Reference
In-Depth Information
All wrybill pairs laid two eggs. Of the 41 nesting attempts that were followed, six
failed due to flooding and eight were lost to predators at the egg stage. In addition 18
chicks were suspected to have been lost to predators. Overall, the 30 pairs produced
29 independent fledglings during the season despite 12 pairs failing to produce any.
The second of the three seasons of monitoring started in late August 2012 and
many of the same pairs have been followed in this second season which had just
finished at the time of writing. The season was marked by large floods in contrast to
the first. Losses of nests and chicks to floods was by the far the greatest influence on
wrybill productivity. Twenty-two nests were flooded and only three lost to predators.
Overall 34 pairs produced 14 fledglings, with 24 pairs failing to produce any.
In contrast, five SIPO nests were lost to floods and the remainder of losses were
believed to be from predation. Overall, 33 pairs produced 19 fledglings with 19 of
the pairs failing to produce any.
While the outcome of the predator control can only be confirmed once the
required 5 years of post-control monitoring has occurred, interim results indicate
that there is considerable margin for improving breeding output by markedly reduc-
ing predator numbers in the Upper Rangitata. The local community is also very
keen to see the pest control begin.
Such a predator control program will involve elimination of black-backed gulls,
poisoning of rats and setting kill traps for stoats, cats and hedgehogs. The planned
program has the potential to offset more than the possible losses from blade strike
while traversing the HMR wind farm. The Rangitata is a major stronghold for
breeding wrybill so while the program will have to achieve an additional four fledg-
lings to offset possible mortalities, it is likely that up to an additional 100 additional
fledglings may be produced each season. In addition there are approximately 120
pairs each of the “nationally endangered” black-fronted terns
Chlidonias albostria-
tus
and black billed gulls
Larus bulleri
and over 200 pairs of the “nationally vulner-
able” banded dotterel. Consequentially, the mitigation program will provide a major
win-win for shore and river birds.
Conclusions and Recommendations
The potential effect on migratory shorebirds was a major issue at the HMR hearing
for a resource consent to operate a wind farm. Even though the less sophisticated
modelling of likely collision mortality at the proposed Taharoa C wind farm had
demonstrated a similar range of mortalities from 27 turbines, the mitigation required
from that wind farm was only a contribution to a predator control program at a
breeding site. This much larger wind farm was initially predicted by the DoC experts
to produce far greater mortality and hence extensive and prolonged pre-consent
monitoring was demanded before the application proceeded, including the largest
and most complex radar-based bird surveys ever conducted in New Zealand. Using
the data gained from four surveys, and using a refined Band Model, a more realistic
prediction of turbine strike was found.