What is the difference between a male & female kestrel?

A couple of people have asked me how I can tell the difference between the male and female kestrel when they visit my nest box. This clip of both birds visiting, hopefully will show how different they are and how easy it is to tell them apart. They have been visiting today, but only a couple of times. Again the weather has been pretty unsettled and quite windy. The male did spend quite a lot of time sitting in the hedge on the opposite side of the field. I am considering putting a perch in there, to see if he would use it.