"The birds would not have been capable of forcing their way out of the cardboard carton in which they were carried. They were either deliberately released from the carton during flight or freed from the carton by other forces during the inflight breakup."
I thought it strange that they said the birds probably weren't capable of fluttering more than a few feet. Unless they had their wing feathers clipped, they should have been capable of full flight. I have several of these birds, so know how well they can fly.
DF.