I can't say all or even most, but my local feed store, where I got 18 healthy chicks last Thursday, receives all their baby chicks through the mail. The USPS regulations say that for day old chicks, they must be mailed within 24 hours of being hatched. Must be able to be received by the customer within 72 hours. And must not be mailed on a day that they would be received on a Sunday. Perfect world, anyway.... But the Post Office trys to ensure their safety, and that they don't suffer in transit.