folks
as Chair of the OBP Recovery Team I too have been astonished at the lack of
response to our press release of a couple of weeks back [issued via the
Commonwealth Minister's office] from both the mainstream media and the birding
community. I thank Sean Dooley for being something of a lone voice on behalf of
the bird. However, I would like to add some further information that could not
be included in the press release, but is freely available from the recovery
team, and to correct a couple of false statements in Sean's newspaper article.
1. The grim prognosis for the wild population is due to a decline in the number
of females that have attempted to breed during the past few summers, although
those pairs that have bred have achieved more than adequate success rates for
an individual nest - > 4 fledglings per active nest.
2. When combined with the rather short breeding life-span of OBPs [< 6 years,
probably only 3-5 years in most cases], a couple of years of low recruitment
can have a big impact on a small population. Our population modelling shows the
population continuing in a steep decline and hitting zero by 2016. Note that
this is only a prediction, but we have a fair bit of faith in the data and the
analysis, and therefore must take a precautionary approach and assume that it
is accurate.
3. On the other hand, our information about survival rates, derived from
sightings of colour-banded birds [reported to us by our volunteer monitors at
Melaleuca and other birders who come across OBPs], indicates that there is no
problem there. In other words, there is not a critical cause of mortality that
is driving the population down, for example wind farms or lights on the squid
fishing fleet in Bass Strait, or even starvation as suggested by Sean in the
press. Rather, the rate of recruitment to the breeding population is not
adequate to overcome the rate at which older birds are leaving the breeding
population.
This suggests that there could be a problem with habitat quality that is
constraining the ability of birds to achieve adequate condition to successfully
produce eggs. This could be a lack of a quality diet on the mainland during
winter, or on the breeding grounds in the 4-6 weeks that birds have there
before egg-laying in December. Interestingly, in the captive population, where
the birds are given a carefully managed diet, the breeding participation rate
is high.
4. Sean's hypothesis about the role of drought in reducing habitat quality is
quite plausible and the recovery team has considered that possibility for some
years. What can the recovery team do about drought/climate change? Perhaps the
only action available to us is to provide supplementary food to wintering birds
to possibly improve their condition. This we plan to do. Likewise, we will
provide a boost diet for the birds when they arrive back at the breeding
grounds, in an attempt to get more females into breeding condition.
5. All of this greatly increases the importance of our captive population
[currently 167 birds] as insurance against the demise of the wild population.
We need to do a bit of work to ensure that the captive population is as good an
insurance policy as it can be. This includes improving its genetic base by
taking more founder individuals from the wild. This can be achieved with
minimal impact on the wild population by removing a single young from a number
of nests [yet to be finally determined] over the next couple of years. If we
can locate unbanded juveniles on the mainland we may also attempt to catch
those because unbanded birds come from a different breeding population to the
main Melaleuca group, where all chicks are banded in the nest, and therefore
may contain genetic material that is not currently represented in the captive
population. We are not proposing to take adults, as stated by Sean in the
press. Note also that OBPs rarely if ever successfully rear a second clutch in
the wild, so we are not proposing to remove entire clutches to captivity [Sean
suggested this as a better option].
6. We do not share Sean's pessimism about the ability of captive-bred and
released birds to successfully complete the migration cycle. We already have
numerous examples of them doing exactly that, including situations where the
released birds did not have the benefit of wild birds to show them the way, if
indeed that ever happens. Successful migrations by captive-bred birds include
birds released at 2 separate sites in southwest Tasmania in spring and birds
released on the mainland during winter.
For these and other reasons, the OBP recovery team sees captive-breeding and
release as being a critical component of future programs to conserve this
species as a component of Australia's wildlife. That does not mean that we are
abandoning the wild population. In fact we will redouble our efforts to improve
the quality of habitat, in Tasmania and on the mainland.
sorry for the long rant - but these are not simple matters and I wanted to
provide adequate information to allow a better understanding of the situation
and the reasons for the plan of action that the Commonwealth and State
Governments are now supporting.
Peter Menkhorst
==============================www.birding-aus.org
birding-aus.blogspot.com
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