The female would tear the skin and fur off the meadow voles and mice before she brought the food to her young. She was especially meticulous when her offspring were at their youngest. She would land at the nest box, look around to make sure no predators were watching her entry, and then disappear into the box. I imagine she would tear the prey into bite size pieces for the babies at that time of their development. Since the Kestrels do not remove anything from the cavity, it makes sense that they did this beforehand.