‘Endothermic vertebrates tend to be represented by larger forms in the colder parts of their range than in the warmer parts’.
I was thinking about this when consulting Schodde’s Directory of Australian Passerines recently. There is much discussion under Australian Magpie as to whether white backs and black backs define subspecies, but Schodde doesn’t comment on the fact, which he reports, that Tasmanian Magpies are smaller than mainland forms contra Bergmann’s rule.
Similarly he notes that the two subspecies of the Eastern Yellow Robin vary by Bergmann’s rule within each population, but doesn’t comment on the fact that the northern spp is larger than the southern.
Shouldn’t both Magpie and E Yellow Robin be split on account of this?
John L
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