90% sure thats a lanner by the head colouration Kestrels are much darker, the size would be a dead give away but I have nothing to compare it to. The shape of the head /beak looks "wrong" for a Kessie from that angle at least
A kessie is about 13" long
a Lanner is about 18" long
There is a possibillity if it is a display bird that it might even be a peregrine x lanner hybrid