Some interesting discussion, but Graeme and others I think it is rather
premature to be drawing the boundary delimiting Spotted Scrubwren from
White-browed. In particular, note that Kangaroo Island’s ashbyi aligned with
eastern birds on mitochondrial DNA in the recent Norman et al paper, though the
authors did recommend leaving ashbyi in maculatus (on morphological evidence)
pending further study of this glaring problem. Also note that on measures
(bill, wing, tarsus) ashbyi aligns with eastern birds (rosinae) not mellori
(see DAB), and that island forms often tend towards melanism.
There is plenty of morphological evidence of intergrades or historical
introgression between the various subspecies in SA, as discussed at length in
DAB and HANZAB. Clearly nailing the species boundary (+/- a hybrid zone) will
require a multilocus genetic study with much better sampling across the whole
area. Breast spotting, eye colour, etc just aint going to cut it. HANZAB
discusses iris colour and suggests that though there is a broad geographic
pattern, it is also variable within subspecies; also that south-western
maculatus of wet forests do indeed have a yellower eye, suggesting it is
habitat driven thus less useful for species circumscription.
Cheers
Martin
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