Why can't chickens swallow while upside down?

Answer 1

Chickens swallow differently than we do. We close our mouths and let our throats do the rest. Chickens open and close their mouths rapidly while tilting their heads up, they need gravity to do the rest.

Answer 2

Chickens have a flap in their throat that blocks food and liquid from entering their airway when they are upright. When they are upside down, this flap does not close properly, making it difficult for them to swallow.