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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