The store doesn't know. I asked. They were mixed in with all sorts of others including peking and mallards so it looked like the store just got a hodgepodge. I've never had runners of any kind or cayugas so I'll be happy with either.
They are definitely black. I'd assume they are very young. Tractor Supply had only gotten the shipment that morning and opened about an hour prior and there were only four of these little guys left when I got there.
It seems that Cayugas and chocolate Runners look similar :/ guess time will...