its in the waitakeres near auckland, i've heard from a friend of mine, he is part of the forest and bird society, not sure who identified it but I expect its been identified correctly, we don't have anything else like that flying around NZ other than falcons...
i'm not aware of this happening before...
various aussie birds get blown by storms. we've got a group of pelicans that came over last year
http://www.birdingnz.net/forum/viewtopic.php?f=9&t=3037