Peter and others
My knowledge of Orange-bellied Parrots is limited to what I have read here
and there, and I have yet to see one in the wild (I hope that I will and I
really hope that my new grandson will too!). However, one thing that
strikes me is that Orange-bellied Parrots (and Swift Parrots) would have
had very different migratory paths, obstacles and food source locations in
the not so distant past when the sea level was lower.
The link to Sahul Time - http://sahultime.monash.edu.au/ - will get you to
an application that shows how the coastline has changed over time. The
current coastline (with minor changes through erosion and sedimentation)
stabilised approximately 5,000 years ago and, before then, Bass Strait was
narrower, or did not exist, and there was generally more coastline with
potentially more feeding habitat for Orange-bellied Parrots. Of course,
the increased aridity during glacial maxima could have reduced feeding
habitat unless the increased flow in major watercourses (from snow melt)
compensated for the generally dry conditions through the creation of
extensive estuarine saltmarshes. This all changed 120,000 years ago when
the world was a warmer, wetter place with higher sea levels than at
present.
The point to this is that Orange-bellied Parrots have been faced with a
very different environment in the last 5,000 years and attempts to
ameliorate recent and rapid environmental change and habitat reduction may
not be going far enough.
Unfortunately, I could not get to Sean's Lunchbox/Soapbox today but I will
read the article in the train on my way home.
David
"Peter Menkhorst"
<
t.au> To
Sent by: <>
birding-aus-bounc cc
Subject
[Birding-Aus] the plight of the
05/05/10 01:39 PM Orange-bellied Parrot
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
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