The photograph below is a really good example of the difference between the sexes, even at such a young age the difference between females and males is clear. The female (left) is darker grey on the wing, the male (right) is much paler.
On the inside wing of the female we could already see the black spots - another characteristic to look for.
The majority of the boxes have been covered now, with the sites left to the last the ones thought most likely to be un-used due to previous years, and so for our last day of box checking we were pleasantly surprised to find 3 more broods of Kestrels - all of different ages which was interesting to see. The other boxes checked were either empty, taken over by Pigeons or the boxes no longer exist - a job for the autumn!