A.) Go under Mom as much as possible, and stay so completely hidden in her fluff as to be undetectable. And quite dry. This also means that your sudden re-emergence shocks any passing by into thinking that chickens do in fact have live births.
B.) Sit on top of Mom as much as possible if she is under shelter to avoid getting in the mud. With practice, you will be able to maintain this position even as Mom eats- no small feat, that.