I spent a long time at Jilava which is an underground prison, and I experienced this phenomenon. The cells communicate with the ditch that connects to the area above, and in the summer the windows are open. For years swallows have been coming and nesting in the cells. There is a light that burns day and night because you are not allowed to stay in the dark, one of the great desires being to eventually sleep with the light off because you have to be under constant surveillance.
So, above the entrance light there was a small platform where swallows made their nests. Well, every spring each swallow came exactly to its nest from the cell, out of the hundreds of cells that were there. They had become tame, and the older inmates had marked them on one leg in the fall, and when spring came they would cup them in their palms and look at the mark on the leg.
So, if a swallow knows how to find a cell, how could it not know a prayer? Therefore, if it’s gone somewhere, on a journey far away or has run away from home, is lost in the world, and you don’t know where it is, if you’re a mother and it’s your child and you pray for him be sure that prayer is the only thing that knows his address. This is one of the miracles of prayer: it never gets the address wrong!
Excerpt from Prayer, a Source of Power in the Trials of Life by Metropolitan Bartolomeu Anania, Doxology Publishing House.