Wednesday, 13 October 2010

More Blue-Tails

With the unprecedented influx of Red-flanked Bluetail in recent days I had my head in a book last night, it used to be a book anyway but BBi makes it all so much easier to find, I digress. Back as far as 1973 the continued western spread of the species into Finland was noted and written about by Finnish birder/scientist/legend Heimo Mikkola in BB. It is interesting that back then they were reporting that this creep west had been more pronounced in years with warm springs as these helped prolong spring migration.
With climate change perhaps still relatively unheard of HM theorised that this spread west may actually be a recolonisation of former territory that had been abandoned during the last Ice Age.
With the continued warming that has happened since that time (whatever the cause) it may then follow that we can expect an increase in the ocurrence of this most magnificent of migrants and perhaps more years where we get significant numbers.


Andrew Kinghorn said...

Interesing read Alan. Thanks for posting.

Anonymous said...

So how many have there been in Britain this autumn? 15 or so? And how many more not found? Considering in Northumbs, probably less than 1% of the coast (and hardly anywhere inland) has been checked intensively, I'd suspect lots, likely hundreds UK-wide.

Also heard of one in Ireland, two on Heligoland (Germany), four on Utsire (Norway) and "lots" in Sweden.

The map in Collins Bird Guide shows the Finnish ones as disjunct from the main Russian population - could (like Blackcaps; c.f. Brit. Birds 96: 427-438) a migratory divide be evolving with the Finnish ones migrating southwest to winter in western Europe, hiding away in dense forestry plantations where no-one ever looks for birds in winter?