Our Kestrel in Britain is a challenge to photograph. Perched, its not too confiding although, on the odd occasion it will allow you close, say, in the car. However, flying is different challenge. When its not travelling fast it might be hunting and give you a chance since is is superb at that skill. The big problem is that is will always face into the wind. Often that means the light will not be ideal; You have no choice.
In December the light is very poor or quite directional. Last week we got good light and a confiding bird. In just one picture the tail fanned and caught the light at the same moment as the wings were fully open. Perhaps my favourite picture of a Kestrel.