While vacationing (and birding) in the UK this summer I was surprised by
the number of species that occur there and here on the West Coast.
Examples: Winter Wren, Barn Swallow, Bank Swallow, Long-eared Owl,
Short-eared Owl.

I am curious how these species became so widespread. I assume they existed
in Europe and Asia and then spread to N. America. As I can't see Winter
Wrens and Short-eared Owls making it across the Atlantic, against the
prevailing winds, in sufficient numbers to establish breeding populations
there must be another answer.

I have no Asian field guides, so don't know whether these species occur
there. If they do, could they have reached N America via the Alaska/Asia
land bridge that existed between the last two ice ages?

If not, I'd be interested in other theories.

John Chandler
Alandale Training Corporation
Richmond, BC, Canada
Phone: 604-274-8777
email: chandler at uniserve.com