The Mallard, Anas platyrhynchos, and Mallard-Black Duck, Anas superciliosa rogersi, Hybridization

The buildup of mallard and mallard-black duck hybrid populations in Australia has caused concern for the conservation of the black duck. Mallard populations are shown to be restricted in size and distribution in comparison to those of the black duck. Hybrids could not be confidently identified, other than those that showed obvious plumage characteristics of both species. Limited field studies in the Sydney district showed the stability of mallard and hybrid populations in comparison to those of the black duck, and there was evidence of restriction of pairing to intraspecific or intrahybrid matings and of poor hybrid breeding success. At present mallard hybridization per se does not pose a conservation threat to the black duck in Australia. This assessment might not apply under large-scale increase and perhaps husbandry of the feral mallard. In sufficient numbers mallard might threaten populations of the black duck by a different means, competition for refuge in times of drought.