I’ve now seen both male and female Kestrels fly into the Monk Parakeet nest several times over the years. They don’t spend much time there. I’ve never seen them emerging with prey (I’ve never seen a baby parakeet here). There’s evidence that these small falcons use parakeet nests as places to roost overnight in Florida. I wonder if they do the same here? Need to be there at twilight…
Backyard and Beyond 
I wonder if Monk Parakeet in on the menu? Kestrels have a varied diet and parakeets probably taste like chicken. Not a big stretch in my way of thinking.