ALM Note: Pest Waterfowl: What Impact Do They Have?

Ponds are a focal point in many public openspaces. Waterfowl including ducks are the most recognised animal to be seen on the urban waterway. Ducks all appear much the same, only the enthusiastic naturalist or trained observer can discern individual species and the subtleties of the hybrid duck. But there exists an underlying struggle taking place at the genetic level between native duck species and introduced waterfowl. The native Black Duck and introduced Mallards (there are 30 derived duck types from the Mallard) have the ability to interbreed and produce fertile offspring further exerting a negative impact on the population genetics of Black Ducks. In NZ the Black Duck population is greatly reduced - to an extent that the Black Duck species in NZ is threatened. On a more immediate level hybrid and introduced ducks display different foraging and migratory behaviour that results in longer stays at the waterbody. Grazing pressures on food associated with a pond or waterway is enormous with little time for the population numbers of food species to recover . Bird populations are artificially supported by augmented feeding regimes commonly seen when parents bring their children along to feed the ducks and enjoy a wildlife experience. The result is a quickly established high density bird populations. Avian diseases spread rapidly and are ruthless once unleashed within the waterfowl population, dramatic population crashes and distressed park visitors often result. Salmonella and viral infections that originate in the local duck population are an often underestimated risk to park users and the responsible land manager.