Would the urine of an eight-year-old protect my chickens?

I was predicting in a recent column that the arrival of spring would be bad news for my poultry, and so it has turned out: two ducks, a fat, waddling Silver Appleyard called Doris and a graceful, elegant little call duck called Marina (the loyal partner of a still-surviving drake called Boris), have disappeared, almost certainly victims of a marauding fox in search of food for its new cubs.