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.
===============================
To unsubscribe from this mailing list,
send the message:
unsubscribe
(in the body of the message, with no Subject line)
to:
http://birding-aus.org
===============================
|
