i think a lot of it's to do with birds that are not 100% health wise,they are disorientated before liberation and head in the wrong direction,to me y/b's are like sheep and will hold onto the company they're flying with,by the time the healthy birds realise they are way of their line which according to birds reported can be up to 200miles away hence exhaustion sets in and dehydration and i also feel that the feeding of the modern day racer doesn't allow for mistakes i.e not enough bodyweight (only talking about y/b's here)