Hi Andrew, The species that always springs to mind to me is the Mandarin Duck (Aix galericulata). Getting to be rare in its native Asia, but increasingly common in parts of Europe (especially southern England). However, I'm not aware of it causing any ecological or economic harm in its introduced range.
Cheers Andy Wilson Assistant Professor Environmental Studies Campus Box 2455 Gettysburg College 300 N Washington St. Gettysburg PA 17325
