I, too, am interested in the issue of competition between honey bees and native
bees.  My research is currently focused on cranberry and highbush blueberry
pollination.  I have been evaluating the abundance and diversity of pollinators
on these two crops.  Bumble bees are quite numerous on the cranberry bogs in
Southeastern Massachusetts.  But I've often wondered what happens to their
foraging success when hundreds  of colonies arrive in an area over a very short
period of time.  This apparent increase in competitors must have some effect on
them.  Wish I had the time to explore this issue, as I think it produce some
interesting results.   Kenna