Bergmann’s rule

["Philip Veerman" <>]

My take on this is that Bergmann’s rule, like several others, is a generally observed phenomenon. Note words “tend to be”.  It doesn’t always apply and neither should it. There are many other factors operating. I recall some research by I think Jane Hughes if I recall that correctly, that our Magpies vary in many genetic markers, of which few if any correlate to the differences in back colour. Why the book may not comment on these 2 examples, you would probably need to ask the authors.

 

Philip

 

From: Birding-Aus [ On Behalf Of Casimir Liber
Sent: Sunday, 26 December, 2021 4:43 PM
To: calyptorhynchus
Cc: <>
Subject: Re: [Birding-Aus] Bergmann’s rule

 

Hi John,

agree that this is a really interesting observation of both taxa. There has been genetic work on both those species (complexes) that shows the situation is more complex. In a rush now but someone else more knowledgeable may expand (or I will tomorrow)

cheers

Cas

 

On Sun, Dec 26, 2021 at 4:33 PM calyptorhynchus <> wrote:

‘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

 

--

John Leonard
Canberra
Australia
www.jleonard.net

Make nature great again.

 

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