Hi Mark
I would say that Kestrels are much less common than Sparrowhawks in an urban garden but they do occur sometimes.
I would describe my garden as semi-urban but it's still fairly built up. One day to my surprise a Kestrel appeared from nowhere, grabbed a Sparrow, perched briefly and then flew off with its prey.
However, I see Sparrowhawks quite often.
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Tony
My Flickr Photostream
Hi Mark, I'm in Mitcham and I've only once seen a Kestrel in the garden. Sparrowhawks visit on a fairly regular basis. I'm sure someone will add a more technical comment, but I think the hunting techniques of the two species are what would cause one to visit and the other to remain in more open areas. Kestrels will feed on large insects as well as small rodents and very occasionally, small birds. They tend to hunt in open areas. Sparrowhawks are able to dive headlong into bushes and trees to get their prey (as their name would suggest) and can hunt in an urban environment.
Unicum arbustum haud alit duos erithacos
(One bush does not shelter two Robins)
Zenodotus (3rd Century B.C.)
Well, I've saved a young kestrel once as it was raining and it was wet but I think they do come to gardens once in a while, personally I haven't seen one in my garden but sparrowhawks tend to be visitor but I think more kestrels come to your garden if you have lots of mice, voles or other small mammals.
sorry if this comment doesn't help, I'm not to sure myself!
Thank you for your comments - very interesting.
Perhaps it was a sparrowhawk - I shall have to observe more closely next time.