Oh, sorry, Hap! I lost this thread momentarily.
Irwin, et al.,
Nature vol 409, pp 333-337 (2001) is the article on
Phylloscopus trochiloides, the greenish warblers that have subspecies around in a ring. You might ask your counterpart why they only "degrade" at the north edge of their range, though. If he says "because they were living under Godless Russian Communism," give up on him.
This message has been edited by Coragyps, 10-31-2004 09:33 PM