John Leonard asked about the number of OBPs surviving in the wild. Its actually
quite difficult to determine the population size of this species because
breeding takes place in the south-west Tasmanian wilderness area where walking
is the only means of access away from the Melaleuca airstrip, and in winter the
birds spread out along about 1000 km of mainland coast. However, we do know
that 80-100 birds return to the main breeding area at Melaleuca each year, and
some 60-80 young are produced there each year. Small groups are known to breed
elsewhere in sw Tas but the number of nests found is very small [not surprising
given the terrain and dense veg]. Most young born at Melaleuca are
colour-banded, yet a reasonable proportion of juvenile birds sighted on the
mainland each winter are not banded, indicating that quite a number of young
are produced away from Melaleuca each year, but we cannot know how many.
To make matters more difficult, the efficacy of winter counts has declined
steadily over the last 10-15 years, ie the proportion of the known Melaleuca
population that we find on the mainland in winter is now only about 10-20%,
compared to about 50% during the early 1980s. So we have given up on using the
winter counts as an index of total population number.
So, a reasonable estimate of the total population size is a max of 120-150
adults, plus perhaps 100 juveniles, in March each year. By Nov each year when
the birds return to the breeding grounds the total population is down to
perhaps 150-180 birds.
More details can be found in the 2008 State of Australia's Birds report issued
by Birds Australia in December [and to be launched by Peter Garret in Canberra
in 3 weeks].
I have been busy this morning liaising with Healesville Sanctuary about the
fire threat to the captive population of OBPs and Helmeted Honeyeaters which I
am pleased to say are now on their way to safe housing at Melbourne Zoo until
the fire threat recedes. Healesville's captive populations of Tas Devils and
Mountain Pygmy Possums are also being relocated.
Peter Menkhorst
OBP and Helmeted Honeyeater recovery teams
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