I'm not great with with magpie genetics, but I believe it's recessive? So both would need to be / carry to get magpie offspring. I'm assuming you have a black magpie, so that along with the broken black would likely mean you will get blacks and broken blacks, possibly other colors depending on recessives they carry.
A black and white magpie carrying no other recessives would be AABBcchdcchdDDejejenen
A broken black (assuming they carry no ressives) would be aaBBCCDDEEEnEn
According to this website, all your kits will be broken chestnuts