I haven't played with rfid tags or bluetooth beacons myself but I could imagine a solution build around one of the two technologies. I think it should consist

I haven't played with rfid tags or bluetooth beacons myself but I could imagine a solution build around one of the two technologies. I think it should consist of an entry tunnel with two sensors, one at each end. The tunnel and the two sensors could be used to determine the direction the chicken goes. It the chick first triggers the inner and then the outer sensor it is checked out and when it goes the other way its checked in.