Or, just use whatever you have, if you already have some orphan blocks. The chicken details can easily be adjusted for size, but it's not actually necessary if the blocks are within an inch or two of 4". Just use your best judgement - if the beak and comb look comically small or large (and not in a good way) size the pattern on a copy machine, or just free-hand it. (Or, do something else entirely.)
I defy you to not have an entire flock of these cuties by the end of the week. Log Cabin block or plain, they're addicting.
*pics of my own creation added after-the-fact*