Tasmanian birdwatchers are being alerted to a serious threat to one of the state’s best-loved ducks.
The Pacific black duck is losing the unique character that defines it by inter-breeding with a duck from Eurasia, the mallard.
The black duck of Australasia (Anas superciliosa) is the common species that frequents all types of water, from city parks, to isolated forest pools and tidal mudflats.
It is not black but chocolate-brown, with shades of pastel-yellow around the head and a horizontal black stripe highlighting the eyes. There are also blue-green iridescent patches in the feathers of the wings.
The introduced mallard, however, is markedly different. The all-brown females might at a distance resemble black ducks but they have bright orange feet instead of the local species’ grey or dark brown. The male duck has an iridescent green head on a generally grey body, with a distinctive white ring around the neck. It also has a curly tail, something missing in the Australian ducks.
The mallard (Anas platyrhynchos) was introduced to Australia in the 1860s and has been spreading slowly across the country, and producing hybrids with the black duck.
Such is the concern about in-breeding that a Facebook page has been created to aid birdwatchers to identify the hybrids. It can be found at https://www.facebook.com/groups/mallardstasmania.
Mallard crossbreeding has led to the near-extinction of the Pacific black duck in New Zealand through the loss of its genetic identity. In many parts of Tasmania, Birdlife Tasmania says it is becoming increasingly difficult to find black ducks without some mallard traits. Black ducks are now extinct on Lord Howe and Norfolk Islands because of hybridisation with Macquarie Island not far behind.
The easiest hybrid trait to recognise is the colour of the legs and feet. Hybrids can have bright orange legs like the mallards, instead of the grey of the black ducks.
Hybrids generally show lighter colours and in males shades of green in the head and the white ring around the neck is prominent.
The Facebook group’s aim is to raise awareness of the hybridisation issue so public support can be mustered for mallard removal by councils.
Duck lovers are urged to take photographs of hybrid ducks and upload them to citizen science websites so that the data can be used to monitor black duck populations affected by mallard hybridisation.
The group acknowledges that the public loves feeding ducks in city parks and opposition to mallard removal through lack of awareness remains a roadblock to assuring the genetic integrity of the black duck species.
The fate of the black duck has emerged at a time of year when the controversial duck-hunting season is underway although the hunting of black ducks, the most common duck species and one of the five species allowed to be hunted under licence in Tasmania, is not under threat from wildfowling.