In a message dated 9/7/2006 12:58:32 PM Eastern Standard Time,  
 writes:

25 years  seems like a long time but it is probably too short.  Many 
introduced  species seem to thrive for that long or longer and then suddenly die  out. 
Dave - Could you give some more examples of the "many."   I can  only think 
of a couple off the top of my head.  Black Francolin, European  Goldfinch and 
maybe Blue-grey Tanager.  
 
Bob Mumford
Darnestown