Suburban red kites

We moved into a new house a week ago, in a suburban area with a lot of red kites which swoop over the houses all day long. In the last week we haven't seen or heard any of the usual garden birds we'd expect to see, other than the occasional over-flying pigeon or crow, and quite a few swifts. Is it possible that the continuous presence of kites is inhibiting smaller birds from visiting the garden? And why do kites seem to favour urban environments so much? Could it be that someone is supplying them with food, or is there sufficient food naturally available to them in such an environment?