Where does one draw the line with exotics? What about species that are not
introduced by transporting them to a new area, but are none less human
assisted. For example, species that have expaned their ranges due to human
habitat modifications (barred owls). There is a well documented northward
expansion of the bush tit's range into Vancouver BC during the last century
as coniferous forests gave way to deciduous second growth. Is the bush tit
an exotic here?

Fred



In addition to spacial introductions, there are also temporal invaders.
The vast conversion of old growth coniferous