I shared your interesting e-mail to Birding Aus with a friend of mine,
Dr Ernest Garcia (a distinguished ornithologist and co-author of
the Handbook - The Birds of the Iberian Peninsula).
He said that you may find the following paper of relevance to, at least, part of your query. I have not accessed the full paper myself, but the abstract reads as follows:
"The song dialect situation of the Redwing, Turdus iliac, in a 765km sq area, 40km north of Oslo, is described based upon registrations during the years 1971-77.
The dialect areas are shown to be small, with sharp boundaries between them. Where two dialect populations come into contact some males may sing both dialects. The conformity and stereoypy within the dialect area with regard to song pattern's is high, and
in general, the dialect structure was constant from year to year. Preliminary colour-banding investigations indicate that Redwings, to a very small extent, cross over to the adjacent dialect area."
One of the authors is/was an academic from Trondheim University.
Song Dialects in the Redwing Turdus iliacus
Tore K. Bjerke and Tron H. Bjerke