This pair of leucistic Mallards flew in with 4 other normal Mallards. Both had greenish olive drab colored bills indicating females. All birds in the group were hatching year birds. The adult leucistic Mallard that has been around a few years courted and mated with a normal female earlier in the spring and I feel these are probably from that mating. The male adult was there that day in the far corner of the pool. See next image.