You can ask the post office by going to their
Contact Form and filling it out. Just ask them what the procedure is for shipping live poultry, and whether their is any age limit, such as you may only ship day-old chicks. I honestly have no idea about shipping older chickens. Good luck! Let us all know what you find out.
I just wanted to add that I suggested emailing because this is the info it gives for calling (I avoid calling if I can email, that's just my opinion):
General Information / Complaints (24 Hour/Live Person)
The Integrated Voice Response (IVR) system is the telephone system that provides automated USPS
information.Call 1-800-ASK-USPS (1-800-275-8777) if you need to put your mail on Hold, if you would like to schedule a Redelivery, if you have a question, compliment, complaint, or suggestion , or help you find whatever you may be looking for, you go through the following options:
Greeting - "Thank you for calling the United States Postal Service."
Language Choice Press 2 for Spanish; if you press nothing, it defaults to English.
You then go into the main IVR menu. The system prompts you for a verbal response (where you state the phrase and the system translates the vocal choice).
The five (5) main IVR menu options and a couple of sub-options are as follows:
Find a ZIP Code
Get Mailing Rates
Track and Confirm a Package
Delivery Services
Hold Mail
Change of Address
Request a Redelivery
Post Office Information (Post Office Hours and Locations)
Delivery Assistance (For Assistance With Delivery of Your Mail)
More Options
Change of Address
Passport Information
Buy Stamps
Post Office Information (Post Office Hours and Locations)
Other Information (For Complaint, Compliment or Suggestion) [this transfers to an Agent]
Live Person Hours of Operation-
8:00 a.m. to 8:30 p.m. Eastern Time (7:00 a.m. to 7:30 p.m. CST) Monday through Friday
8:00 a.m. to 6:00 p.m. Eastern Time (7:00 a.m. to 5:00 p.m. CST) Saturdays
Closed Sundays and Holidays (2007 Postal Holidays )