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Duck plague (also known as duck viral enteritis) is a worldwide disease caused by Duck enteritis virus (DEV) of the family Herpesviridae that causes acute disease with high mortality rates in flocks of ducks, geese, and swans. It is spread both vertically and horizontally—through contaminated water and direct contact.
Facultative lagoon (polishing pond) providing tertiary treatment after a constructed wetland in Hamburg-Allermöhe, Germany. Overflow from the facultative lagoon may be routed through one or more polishing ponds supporting lower populations of anaerobic micro-organisms and a higher proportion of aerobic organisms adapted to survival in lower concentrations of organic material.
The ducks are frequently observed along canals where large and overhanging Acacia trees provide shade and cover from predators and a haven in which to feed and rest. The quiet and still water in the canals of the plantations provides an undisturbed and secluded location, away from local communities which may hunt the ducks or collect their eggs.
Ducks eat pests (e.g. brown planthoppers) in the crop; they stir water, limiting weeds, and manure the rice. Surface must be even; water depth must suit ducks; young ducks best as they don't nibble rice leaf tips. [5] Rice-fish-duck: China: Fishes bred on rice terraces: Fattens ducks and fish, controls pests, manures the rice.
This polyculture yields both rice and ducks from the same land; the ducks eat small pest animals in the crop; they stir the water, limiting weeds, and manure the rice. Other rice polycultures in the region include rice-fish-duck and rice-fish-duck-azolla systems, where fish further manure the rice and help to control pests. [15] [16]
The Pacific black duck is mainly vegetarian, feeding on seeds of aquatic plants. This diet is supplemented with small crustaceans, molluscs and aquatic insects. Food is obtained by 'dabbling', where the bird plunges its head and neck underwater and upends, raising its rear end vertically out of the water.
The canvasback feeds mainly by diving, sometimes dabbling, mostly eating seeds, buds, leaves, tubers, roots, snails, and insect larvae. [3] Besides its namesake, wild celery, the canvasback shows a preference for the tubers of sago pondweed , which can make up 100% of its diet at times. [ 12 ]
The diving ducks, commonly called pochards or scaups, are a category of duck which feed by diving beneath the surface of the water. They are part of Anatidae, the diverse and very large family that includes ducks, geese, and swans. The diving ducks are placed in a distinct tribe in the subfamily Anatinae, the Aythyini.