Here's some info on that for you:
http://www.huffingtonpost.com/2009/09/01/chicks-being-ground-up-al_n_273652.html
http://www.oregonlive.com/pets/index.ssf/2010/01/pet_talk_as_backyard_chickens.html
My shipment from McMurray last year arrived in Oregon the next day, on a Sunday. The sort facility 30 minutes north of us called me to let us know we could come pick them up.
I can say though, from the perspective of a business owner who ships all orders with USPS, that the routing and delays...