Red kites are more scavengers than birds of prey (they used to live in London, a few hundred years ago & scavenge all the rubbish that people threw out on to the streets!). Although they're big birds, their talons aren't that strong, so they can't bring down large prey like, for example, a buzzard can. Their main food is small mammals, frogs, worms & the like, and, of course, carrion. I must say, I think it must've been lovely to see them following the tractor! We've got loads of kites here in west Wales, but I've never seen them following a tractor - we don't have much arable farming here, so that's why.