Duck Anas platyrhynchos

This entry is the mallard-derived domestic duck, Anas platyrhynchos, of which the Pekin is the dominant meat type; genomic work on Chinese breeds shows descent from the mallard with introgression from the spot-billed duck, A. zonorhyncha. Ducks are kept for meat, eggs and down. FAO describes them as hardy, disease-tolerant foragers suited to wetland rice systems, where they can range by day and be confined at night because they lay most of their eggs within about three hours after sunrise. Breed weights run from Indian Runner at 2.0 kg for drakes and 1.8 kg for ducks to Pekin at 4.1 and 3.6 kg, and Khaki Campbells reach 90 percent hen-day lay with 73 g eggs. Incubation takes 28 days. The clinical fact that separates ducks from other poultry is their place in influenza ecology: mallards are a natural host, and experimentally infected birds stayed active, ate normally and gained weight while shedding virus continuously for a mean of 12.0 days by the faecal-oral route. Silent shedding lets duck flocks seed H5 and H7 viruses that can become highly pathogenic in chickens.