General Discussion : Attracting Kestrels to a previous site

It's not uncommon for nest boxes to go unused. There can be any number of reasons. The decoys won't influence acceptance of the box as a suitable nest site, so dont waste your time. Instead, concentrate on whether or not the basic elements of habitat are still right. Most likely the shrubs and trees have grown too high over time. The Kestrel needs open ground, like pasture, with crop cover no higher than about one foot; and a place to perch, either a tree or most often a power line.If you can relocate the box to a better site, do so. Remove old boxes as they just breed box competitors, which almost guarantees more stress on your Kestrels.
There should be an unobstructed flight path in and out of the box. Insect parasites lay eggs in the bedding, so it's important to clean out last year's bedding material and relace it with new wood shavings or chips, about one or two inches deep is enough. The Kestrel doesn't bring nest material to the box, so any material added to yours is a clue as to what species might be occupying your box and preventing Kestrels from nesting there.
If your box is old with holes or cracks, or the door is warped and won't close tightly, replace it. If drafts cause the chips to fall out and the floor goes bare, those eggs will roll around and never hatch. It's an ecological trap to invite
birds to nest in a box that will surely cause the nest to fail. Dilapidated boxes cause more harm than good and are part of the problem, not the solution.