We have chickens and ducks at our house. First of all if you get chicks they will not start laying for 4-5 months. After that it will be spotty for a while.
Chickens are loud and stink. You wont have to worry about a foreign country, they will be dead by your own hands long before the first port.
Will hanging them over the stern rail violate any no discharge zones?
On a positive note they would probably make good watch dogs