Hi Kevin,
I understand what you are saying, but we must not confuse "habitat" with
"environment". I agree that similar habitat for Spotted Scrubwrens and
WBSWs occur in coastal areas of southern/south-western Australia (Spotted
Scrubwren) and south-eastern/eastern Australia (White-browed Scrubrwen), but
the predominant environmental conditions are very different. Coastal
populations of Spotted Scrubwrens are, in general, in hotter and much drier
climates, probably live in saltier environments, and may even have different
diets. Sunlight reflected from the ground always seems much more intense
along the west and south-west coast, than along the east and south-east
coast - as a blue-eyed person who now lives in Sydney, that is something
extremely noticeable to me on return visits to WA. I'm not saying
scrubwrens in the east/south-east don't ever experience those environmental
conditions, I'm just saying that those conditions prevail more in coastal
areas of the south and south-west and are usually more intense. For
instance, if we look at average annual rainfall (from west to east):
Hamelin Station, Shark Bay: 204 mm; Rockingham, WA: 702mm; Eyre Bird
Observatory 317 mm (the three sites where I have studied the Spotted
Scrubwren); Ceduna, SA: 295 mm; Kangaroo Island, SA: 536 mm; Western
Treatment Plant, Vic: 538 mm; Sydney: 1082 mm; Coffs Harbour: 1601 mm:
Brisbane: 1079 mm; Cairns: 2236 mm.
So, even though Spotted/White-browed Scrubwrens are found in similar coastal
habitats, Sericornis probably colonised Australia from PNG, expanded its
range along the east coast of Australia into the south-east, then westwards
along the south coast into the south-west, then up the west coast of WA as
far north as Carnarvon. If that is an accurate picture of the evolutionary
expansion of the distribution of scrubwrens in Australia, then ancestral
stock originated from the tropics/sub-tropics and I still maintain that
Australian environments (not necessarily habitats) occupied by scrubwrens
west of Victor Harbour in South-Australia are marginal for this genus. I
also believe that this is reflected genetically and phenotypically (and
probably physiologically and behaviourally) through speciation of the
Spotted Scrubwren. The purpose of my PhD in the early 1980s was to examine
differences in the physiological and behavioural ecology of what was then
Sericornis frontalis in three different environments of WA: arid (Hamelin
Station, Shark Bay), semi-arid (Eyre Bird Observatory) and temperate
(Rockingham, near Perth). It just so happens that study was conducted in
environments that I would consider to be very marginal for what I would now
term the Sericornis frontalis "superspecies" (Sericornis maculatus +
Sericornis frontalis).
Kind regards,
Stephen
Stephen Ambrose
Ryde NSW
From: Kev Lobotomi
Sent: Tuesday, May 1, 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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