Yes, this should be impossible -- scientists have no idea how they do it: "Current models say the birds should conk out after three or four days, yet they fly

Yes, this should be impossible -- scientists have no idea how they do it: "Current models say the birds should conk out after three or four days, yet they fly for more than a week. “We can’t explain the physiology that allows them to do this,” Dr. Guglielmo said. “We know what the energy costs should be from wind tunnel experiments, but when we try to use our models, the energy costs we know they used are much lower.” The birds use half or less of the energy expected." “Are they going into a suspended animation state when they are doing these monster flights?” Dr. Guglielmo asked. “I don’t think they are in a normal physiological state when they are doing this,”