dont think it could be done, but there is a few ways young birds go missing, !/ bop, (how much) 2/ brought back home with stray baskets (how much)3/ going into other lofts,some reported some probably not, (how much) 4/ being reported by non fanciers in their back gardens,how much 5/ by members (2 0n site i believe) going down south to bring birds back up the road,how much 6/ joining with the streeters and living wild, how much, 2-3-4-5 and six, most are healthy fit birds, why dont they home, ????, bop are a part of losses , but there are a good few other reasons,