Now the species is making a rebound. How so? Trees are maturing and become nesting sites and people are feeding them. These aren't bird feeders like you and I might have. A great paper by Orros and Fellowes in Ibis describe a great study where they surveyed people about feeding them and did surveys of roadkill.
There's about 16 g roadkill/km/day. Sounds like a lot but that's a mouse or two. Garden feeding was much greater at 23 g meat+ nonmeat scraps/km/day. They discuss competition with foxes and rats but not increasing the population with those two organisms, which might have negative consequences for other birds (through nest predation) and human health.
I wonder if this is a synanthropic species - adapted to humans - but at an earlier time when we flung our crap out the windows.
There are a number of videos of Red Kites out there but I like how this shows the high densities you can get as well as their agility. They don't stop to eat!