I'm surprised by that, Rob.
With the Kestrel's liking for hunting along motorway verges I thought you'd see quite a lot of them while doing your driving jobs.
Kestrel's number aren't good at the moment. They are the smallest Falcons, it maybe the fact that some of the bigger Falcons are making a come back it has affected their numbers somewhat.
There are a few reasons for the decline, which has been shocking in numbers (65% reduction in numbers by 2014 in Scotland) I can't find any recent studies, but back in 2014 the change in farming practices has thought to be the major reason, with changes in when seed is planted, they've switched from Spring Barley to Autumn rape, meaning there is less food in winter for voles and small birds, so less of them and therefore less prey. As Jill says, there is also a detrimental effect of the boom in the large species of birds of prey - Goshawks, Owls, Peregrines and Buzzards all prey on Kestrels. Where I live, there doesn't seem to be many birds of prey, not seen the Sparrowhawk for a few years now, we saw one Buzzard last week and that is about it, it is all crows and magpies.
I see a hell of a lot of Buzzards these days, all around the motorways up and down England and Scotland, very common sight now. Around the Oxford area I have seen Kites too since they reintroduced them. Our kid does Southampton to Brum every day and sees nothing but the big falcons.
Be a real shame if we lose the Kestrel.