I actually stand corrected in my opinion of the evolutionary radiation of
Sericornis. I've had a closer look at the scientific paper that initiated
this whole discussion (Norman et al. 2018) and their results suggest that
the PNG species probably arose from an ancestral form originating in
Australia. The Australian ancestral form gave rise to two separate lineages
8.2-10.9 million years ago: the PNG species lineage and the Australia
White-browed frontalis/Large-billed magnirostra lineage. They indicate that
the Sericornis citreogularis lineage diverged from an even more distant
ancestor 11.5-13.0 million years ago.
But I still stand by my original hypothesis that S. maculatus currently
inhabits marginal environments for the genus and that evolutionary radiation
occurred from Bassian ancestral stock in wetter eastern or south-eastern
Australia.
Cheers,
Stephen
Stephen Ambrose
Ryde NSW
-----Original Message-----
From: Jeff Davies
Sent: Wednesday, May 2, 2018 11:15 AM
To: 'Kev Lobotomi'; 'Stephen Ambrose'; 'Graeme Chapman'
Cc:
Subject: Scrubwrens
Agree with Kevin,
The spit is more to do with the Eyrean division than habitat, creating two
species that now maintain there difference with abutting distributions.
Cheers Jeff.
-----Original Message-----
From: Birding-Aus On Behalf Of
Kev Lobotomi
Sent: Tuesday, 1 May 2018 11:12 PM
To: Stephen Ambrose <>; 'Graeme Chapman'
<>
Cc:
Subject: Scrubwrens
Hello all
Everyone here is saying that there is a major habitat difference between,
White-browed & Tasmanian Scrubwren & The Spotted Scrubwren. I don't agree at
all! White-browed and Tasmanian are quite at home in coastal areas and quite
like the scrubby habitat, as long as there's enough vegetation in the
understory. The coastal areas of the Western Treatment Plant for example are
full of White-browed Scrubwrens & this habitat is pretty well identical to
many places I have seen Spotted Scrubwren. Perhaps Spotteds prefer drier
stuff overall, but there are still many habitats that all 3 species share.
Kevin Bartram
Sent from Outlook<http://aka.ms/weboutlook>
________________________________
From: Birding-Aus <> on behalf of Stephen
Ambrose <>
Sent: Tuesday, 1 May 2018 2:31 PM
To: 'Graeme Chapman'
Cc:
Subject: Scrubwrens
Hi Graeme,
The more I think about it, the more I believe the differences are due the
Spotted Scrubwren expanding its range into marginal environments which, on
the whole, are quite different to those colonised by other scrubwren
species/forms. Sericornis is essentially a genus of tropical, sub-tropical
and temperate environments, whereas Sericornis maculatus has managed to
colonise drier and hotter (and saltier?) environments which really challenge
the species' physiology and behaviour. Perhaps Victor Harbour is at the
boundary of what is marginal for scrubrwens, and anything west of that
location, presents more of a challenge and the need for different survival
strategies, which are expressed (in part) as morphological and plumage
differences.
The other striking difference to me is that S. maculatus is quite a bit
smaller than S. frontalis (the body weight of maculatus is typically 75-80%
that of frontalis), which is a further indication that environmental
constraints faced by scrubwrens in the western part of the continent are
probably greater than those in the east and south-east. This supports the
concept that S. maculatus occurs in marginal scrubwren environments.
Cheers,
Stephen
From: Graeme Chapman
Sent: Tuesday, May 1, 2018 10:07 AM
To: Stephen Ambrose
Cc:
Subject: Scrubwrens
Hello Stephen, and others,
Thank you very much for all your information. This has turned out to be a
more interesting subject than I had expected.
I have had an email from a chap who lives near Victor Harbour. He assures me
his birds have yellow eyes. But according to Schodde & Mason, Victor Harbour
birds are subsp. rosinae which are at best White-browed but have "faint
dusky spotting" on the breast - call them what you will, which poses an
interesting question - where does the changeover from yellow to blue (in
adults) occur? or is it even gradual!! I think not.
It will be interesting to learn what Norman, Christidis & Schodde have to
say on the subject. It is a very complicated issue - takes up three pages
(169-171) of discussion in Schodde and Mason.
Cheers
Graeme
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