Hello every body, I'm new in this subject and started raising chickens last year. Few weeks back I placed 4 chicken eggs and 12 chukar partridge eggs under my broody hen. at day 21, the 4 chicken chicks hatched. after 2-3 days the other eggs started hatching, but the hen killed every partridge chick comes out! is that because the differences between the chicks in appearance? or what? any thoughts please.