G'day Chris,
I think we are a long way from being convinced of anything about Tasmanian
Boobooks on the mainland except that they are recorded there.
The real problem is lack of effort to identify the bird in Victoria, most
people don't even know what the bird looks like let alone aware that it
should be looked for. Digital photography will hopefully increase the
probability that it will get photographed on the mainland but if people
aren't aware of the possibility an unidentified photograph will be just as
useless as an unidentified field observation. To this end I am happy to
receive as many photos as people want to send me for identification.
A quote from Kevin Bartram in an email to me last night "there is quite good
evidence that Tas birds migrate to the mainland during the colder months of
the year. I have personally found 3 dead specimens, 2 roadkill & 1
beachwashed, all now donated to the Vic Museum. And there are also several
other specimens collected during the colder months on the mainland". So
there are definitely museum specimens to go with these birds that get
photographed, but I don't think we can say if this represents a migration,
or just an annual dispersal of some individuals, or even if the birds are
Victorian. But they aren't being recorded in the Wet Forests, not yet
anyway, the Hamilton bird is in a suburban back yard, and another recently
photographed dead bird was from Altona 2010(unfortunately it wasn't
collected). But this obviously doesn't mean they aren't in the Wet forests.
What's needed is for people to be aware of and start scutinizing their
Victorian Boobooks for Tassy birds. We need more Kevin Bartram's out there
on the job.
Cheers Jeff.
-----Original Message-----
From: Chris Corben
Sent: Wednesday, 12 June 2013 3:57 AM
To: Jeff Davies; 'Steve'; 'Birding Aus'
Subject: Possible Tasmanian Morepork in Victoria
Hi all
Interesting subject!
So how convincing is the evidence that Tasmanian Boobook is only a winter
visitor to the mainland? Or could it be like Pink Robin, with migration to
the mainland in winter but also breeding in the wetter forests of Victoria
and southern NSW?
I'm particularly interested in this, because the Gould's Wattled Bats of
Tasmania seem to me to be a different species from the widespread form on
the mainland. Migration is unknown, and the Tasmanian form is found in
summer in the cool, wet forests of Victoria and southern NSW, including the
Otways. I don't think anyone agrees with me on this, by the way! But an
interesting side of it is that it seems the habitat of the Tasmanian form on
the mainland is seriously undersampled acoustically, which is by far the
best means for seeing the difference.
Otherwise people would have noticed the difference long ago. The point being
that people who work with bats are vastly more likely to be exposed to the
much more widespread form than the more restricted Tasmanian form.
It might seem this would be less the case with Boobook Owls, but maybe not
if our samples are highly biased. For example, what if a high proportion of
the specimens available are from road kills, then this sample is likely to
be very biased against birds breeding in the wet forests, but less biased
against Tasmanian migrants in winter. It could also have consequences for
our understanding of identification criteria, since if you operate from the
assumption that the Tasmanian birds are winter visitors, then the apparent
distinctness of the form could be diluted by occasional specimens from the
wet forests in summer, seeming to contradict the general view of how the
forms differ. It often turns out that a better understanding of the temporal
and spatial distributions of similar taxa can lead to a clarification of
identification criteria, just as understanding their ID can lead to a better
understanding of distribution.
Cheers, Chris.
On 06/10/2013 10:19 PM, Jeff Davies wrote:
> G'day Peter,
>
> It's the combination of three or four features all in the one bird
> that suggest Tasmanian Boobook, yellow eyes, small white spotting
> surrounding the face and elsewhere if you could see it eg hindneck,
> and as John has said white markings in the belly presenting more as
> overlaid white circles with less of a tendency towards longitudinal
> shapes. Steve Clarke also felt that the bird looked particularly
> small, ssp leucopsis is over 10% smaller than ssp boobook.
>
> Cheers Jeff.
>
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