Chris
> Do you think it likely that your bees obtain their propolis from a single
> source or multiple sources?

What a question!  I have no idea, but would expect that bees would forage 
for propolis as they do for honey and pollen, i.e. over a wide area with 
multiple sources - provided, of course, that more than one source was 
available within flying range.  Perhaps there are some studies that might 
help, but I have not seen any.  Most of the literature on propolis that I 
have seen seems to concentrate on its medicinal properties (for humans).  I 
also cannot claim to have seen bees collecting propolis, other than a bee 
that I once watched removing it from a glove (back in the days before I used 
rubber gloves and soda wash); I suspect that much of it comes from high up 
in trees where it would be difficult for us to observe the bees working.

Best wishes
Peter Edwards
beekeepers at stratford-upon-avon.freeserve.co.uk
www.stratford-upon-avon.freeserve.co.uk/

*******************************************************
* Search the BEE-L archives at:                       *
* http://listserv.albany.edu:8080/cgi-bin/wa?S1=bee-l *
*******************************************************