I have been asked on many occasions how I've manage to locate so many Little Owl sites, well going out in the evening and listening for them has proved to be a great method, second only to actually seeing the birds. As we are now approaching the time of year when the Little Owl will be thinking about establishing new territories and looking for mates prior to the breeding season they become extremely vocal, in particular around dusk.
In order for you to locate your own Little Owls by call alone one must firstly get familiar with the variety of sounds they make. They are not the traditional "twit to woo" that many people associate with owls (Tawny) but a selection of screeches and short high pitched yelps. Here is an excellent link (below) to the "Owl Pages", where samples of Little Owl (and other owls) calls can be heardare.
The owl pages
But remember, before you are going to locate them it is absolutely critical that you are where they are to be found, open countryside, paddocks and orchards with a scattering of hedgerows, mature trees and farm buildings are all good, but not heavily wooded areas!
Good luck and let me know if it helped?