Hi Connor / all
I guess it is a little longer than 3 years since the question of the origin / timing of Red Kites in E Anglia has been a topic of conversation but well done for raising it here.
I saw an untagged Red Kite (dare I say KT?!) over the Scrape at Minsmere whilst volunteering there on 23/03/1996. At that time, the feeling was that any untagged birds were probably immigrants, particularly in places so far from any of the release sites back then. A few more individuals (and a Black Kite) were reported up the coast at Benacre at the same time, so the consensus was that these birds were part of an early-spring influx from the Continent.
I didn't see any kites in Norfolk/Suffolk whilst living at Stowmarket 2000-2002 but since returning to live in Breckland in 2009, my BirdTrack account reveals records on these dates:
Thetford 04/03/2009 (which I jammed during the outdoor part of my interview at BTO that day, sparking a mini-twitch from the office!)
Thetford 24/05/2010
Thetford 25/05/2010
Thetford 11/03/2011
Thetford 25/04/2011
Stiffkey Fen 19/08/2011
Titchwell Marsh 19/08/2011 (presumably same bird drifting along the coast)
There have already been at least 4 records in Breckland in 2012, and a few more from adjacent areas of west Suffolk. I'm sure the vast majority of the reintroduced birds are untagged these days (including those breeding in/near East Anglia), and probably have been for several years, so I would think most, if not all, recent Breckland records relate to birds from the reintroduced population 'on the wander' in spring.
It may be that birds are more sedentary during incubation / provisioning, and perhaps over the mid-winter period too, though obviously it would need a lot more than a few people's records to test this hypothesis...
Cheers
Nick