I do not recommend getting birds at a poultry auction! It is a place where people get rid of the birds they dont want so you can expect problems. It is usually roosters and older hens. All the birds from many different sellers are kept together, Many birds being taken to and from the property each week, It all adds up to a greater risk of spreading any diseases back to your flock. Just for added information the average roosters usually go for about $10 each more for larger ones less for smaller ones. It is really a fresh meat auction. Still interesting to see how it all works and what is available.
I went when I first got my farm and was looking for a few goats to start a small herd. I quickly realized the above rules apply to them as well. It is more obvious with the larger animals as you see more of the old, the sick, the injured and the deformed. I now get young bucks to raise as stud from a local farm. The one in CT is better for poultry and small animals rabbits etc, The one in MA is better for larger animals.