I've seen reports suggesting that chicks are on a parr with rodents as a snake food but a variety or a mix of both is supposedly best of all .
I've got a pair of Cinnamon royals weighing 1Kg each that have been fed a mix of d/f frozen day old chicks - d/f frozen mice - d/f frozen rats in a kind of rotation . They were put on d/f chicks from hatchings .
My other Royals won't touch them sadly .
Also they're about a tenth of the price of mice .