I purchased a Kestrel Nest box from Orchard Guard and Installed in a dead tree last year It located adjacent to the Prime Desert Woodland Preserve in lancaster CA- My previous nest box is currently occupied by honey bees. I have removed the bees twice but they always come back (see my info on ace hardware) So I bought another nest box. Kestrels did not nest last year. But this year it looks like they will nest- Heave seen them in the nest box this 14 March and 20 March observed mating
Image:

Kestrels caught in tha act yesterday 20 March the first day of spring
New to site as well - great to see your apparent success!
Fantastick photos Phillip,
Welcome to this site. Here is our KESTREL KORNER link.
http://www.nu-sun.com/html/kestrel_korner.html
Have a great day,
Nu-Sun Cinema American Kestrel Research Center
Winnipeg, Manitob, Canada