Hi Richard - good to hear from you!
Thanks for your comments re Pink Robins.
And for those who are only interested in things with feathers, now is
the time to delete!
So here's a short history of the Gould's Wattled Bat story, from my
perspective.
In the late 80s, I was doing lots of bat recording in southern Qld, and
one species which I really wanted to meet was Eastern Falsistrelle
(FATA). I knew they were known from some of the higher mountain areas in
the border ranges. One such location was Mt Tamborine, so I went there
one night in the hope of finding them, but without any knowledge of what
they called like. On the highest part of the mountain, I found a
largeish Bat flying repeatedly along a road, and its calls were quite
different from anything I had recorded before. So I assumed this was
FATA, but in the long run, it turned out I was wrong.
Subsequently, I recorded the same calls in Tasmania and at a couple of
localities in Victoria where I had been told FATA could be found. One of
these was Camberville. So I felt even more convinced these must be FATA,
since the calls were distinctly different from any Gould's Wattled Bats
(CHGO) I had recorded elsewhere, and there simply wasn't any other
species known to which they could apply.
Others were mislead by my incorrect identification of these bats, and I
understand that a number of records of FATA were incorrectly based on my
"reference" calls. Such is life, but I personally think that if you
don't make mistakes, you aren't trying hard enough! But not a common
view amongst birders...
Anyway, in the mid 90s, others were getting recordings of FATA and
finding they weren't consistent with my calls. This wasn't totally
convincing to me at first, because the calls I was shown were all based
on recordings of released, captured bats, and at a stretch might have
been compatible with the calls I had associated with FATA. Now, however,
I have had a great deal of experience with FATA in Tasmania and
Victoria, and there is no way I would now think my weird calls were
FATA, and I have often recorded them at the same place.
So what are the "Droopy" calls I recorded at Mt Tamborine? Droopy maybe
an unfortunate name for a cute little bat, but it is a very good
descriptor of how their calls differ from other species. So it kind of
stuck, for me anyway.
I have now spent a lot of time looking for and at Droopy bats, and I
have no doubt they would be identified in the hand as CHGO (but I have
never seen on in the hand). But their calls are different enough from
non-Droopy CHGO to make them easily distinguished in most circumstances.
To put this in perspective, they are much more easily distinguished from
non-Droopys than say Greater Broad-nosed (SCRU) is from FATA or
Scotorepens orion. There we have three different species in three
different genera which are all hard to tell apart, yet Droopys and
non-Droopys are almost always easy.
Droopy Bats live in the cool, damp forests of south-east Australia. They
are the only repesentatives of CHGO in Tasmania, which is especially
interesting since the type locality of CHGO is Launceston! They are
common in the Otways of Victoria, and I have encountered them in the few
places I have looked in the mountains of Victoria, and I found them
common in the forests high in the Snowy Mountains. They seem to overlap
with non-Droopys at some places on the edge of their range, such as
Turourong Reservoir in Kinglake ( at least they seemed to in 2004!).
Tumut in NSW is an interesting case - I spent some time there in Jan
2010. Around Tumut itself, around 300m ASL, I found no sign of Droopy
Bats, but recorded non-Droopys in several places. Up the road from
Tumut, above 1000m, they were overwhelmingly Droopy Bats and were
reasonably common wherever there were trees. Despite the altitude
difference, this is only a few km from the lowlands - I seem to recall
the main climb is only 8 km.
I have also searched for them in a number of other places in NSW where I
thought they might be likely to occur, but without success. I did not
get to the Brindabellas, but would be very surprised if they are not
there. I did not find them in the Blue Mountains, for example, or Mt
Kaputar or the Gibraltar Range, or Ebor, and I have never encountered
them in the Border Ranges or Main Range of Queensland, or in the high
country around Stanthorpe.
Despite this, I have two sets of recordings from southern Queensland,
the original one from Mt Tamborine and a much more recent occurrence
near Blackbutt. I have been to both Blackbutt and Mt Tamborine many
times since, without any hint of Droopy calls.
So what were they doing in Blackbutt and Mt Tamborine if they don't seem
to be in the main habitats between there and the Snowy Mountains? An
interesting question, but one with many feasible biological
explanations. They might have been vagrants or there might be
populations somewhere in the higher country of southern Qld which I
haven't encountered yet, or they might be like Swift Parrots and get up
to Qld sometimes. But there is another possibility - it might be just a
stochastic thing. Since I have done so much recording of CHGO in
southern Qld compared to anywhere else, maybe these are just bats on
the extreme edge of the bell curve, and I was seeing droopy calls from
non-droopy bats. But it is a hell of a coincidence to have first found
these calls at a known site for FATA!
Droopy calls can be recorded from non-droopy bats when flying in lots of
clutter, and likewise, Droopy Bats produce non-droopy calls when in very
low clutter. It isn't like you can always be certain straight away if a
bat is Droopy or not, though usually it becomes obvious if you watch the
bat for a short while. The calls I had from Mt Tamborine and Blackbutt
stood out as very different from the calls I usually see in southern
Qld. It was what the bat typically does which matters, not the extremes
it can produce. This is true of most bat acoustic identification issues.
So what are Droopy Bats? In my view, by far the simplest explanation is
that they are a distinct species associated with the Bassian biological
region. If that's true, it means most Gould's Wattled Bats seen on the
mainland are not really Chalinolobus gouldii, but something else. I do
not see this idea as being far-fetched or in any way surprising, and the
distribution this bat shows has close parallels with some other species,
such as Vespadelus darlingtoni and FATA.
If it is not a different species, then the situation is actually a lot
more interesting, because it means there is something very strange going
on with the echolocation system. Variable as bat calls are, it seems to
me that echolocation systems of individual species are very
conservative, and when differences of this magnitude are found, it is
because unrecognised taxa are involved. Several people have suggested a
number of alternatives, such as the droopy calls are a response to low
temperatures, or high humidity or some other local variable. But do you
really think Tasmania is so consistent that the temperature is always
lower than southern Qld? Of course not. It may be that my observations
are heavily biased by some factor of which I am unaware, which is
causing me to see things this way. But all these things can and should
be tested, and I would put my money on different biological species!
Cheers, Chris.
On 06/12/2013 05:48 AM, Richard Loyn wrote:
Hi Chris, I'm not convinced that Pink Robins make the crossing, in contrast
to Flame Robins. HANZAB says there is no evidence for such crossings, and
Tasmanian birds are subspecifically distinct (slightly longer-winged).
In Victoria (as you know) adult male Pink Robins mainly remain all year in
their breeding territories in cool temperate rainforest or wet mountain
forests with similar structure, along with some brown birds (perhaps mainly
adult females), although they tend to forage in more open situations
(including log landings). A few adult males and lots of brown birds move
into drier habitats for the winter, in foothill forests and in shady
multi-stemmed habitats such as coastal teatree thickets, also in
box-ironbark & regrowth river red gum, etc.
It's a similar story in Tasmania. Reporting rates go up in winter in both
states because birds are more widely dispersed and found in more accessible
places. There are records from Bass Strait islands (King & Flinders),
apparently referring to resident populations of the Tasmanian subspecies. I
don't know of any reports of falls of Pink Robins on Bass Strait islands or
the Victorian coast, whereas such events are quite often reported for Flame
Robins.
I hope this helps a bit. I wouldn't be surprised if occasional Pink Robins
crossed the strait but it seems there's no generally accepted evidence for
it and I suspect it's the exception not the rule. It may be worth checking
various reports of bird observations on small Bass Strait islands.
I look forward to hearing more about the boobooks and the Gould's wattled
bats.
Cheers, Richard.
Richard Loyn
Eco Insights
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