By the funny part of it, why not mix into the chicken food large amount
of Cesium-137 or Uranium-235 powder and use a geiger counter to find out
which chicken site is more radioative?  You could probably recognize
heavier chickens at night, they will literaly "glow" brighter.  This
could be a nice use of nuclear waste material... problem is, you would
need a special documentation of transfer (DOE/NRC Form 741) to transport
those chicken...(classed as nuclear material). hehe

Wagner