Have Patagonian waterfowl been affected by the introduction of the American mink Mustela vison?
The American mink Mustela vison has spread widely beyond its native North American range and is associated with problems for the conservation of native species because of its impact as both predator and competitor. We investigated the impact of feral mink on waterfowl in Lanín National Park, south-west Neuquén, Patagonia, Argentina, an area in which the predator is currently expanding. Statistically significant differences were observed in the number of waterfowl species at lakes without mink (7.3±SE 0.7) compared to those with mink (4.0±SE 0.6). Overall abundance of birds observed per day was higher at lakes without (104.2±SE 20.6) than with mink (21.2±SE 22.3). The great grebe Podiceps major, speckled teal Anas flavirostris, Chiloe wigeon Anas sibilatrix and red-gartered coot Fulica armillata were more abundant on water bodies without mink, and flocks of the ashy-headed goose Chloephaga poliocephala were larger in areas without mink. Other species, such as the white-tufted grebe Rollandia rolland, coscoroba swan Coscoroba coscoroba, black-necked swan Cygnus melanocoryphus, cinnamon teal Anas cyanoptera, Andean duck Oxyura jamaicensis and Andean gull Larus serranus were never observed in areas harbouring mink. We conclude that at least 12 of the 25 waterfowl species observed are sensitive to the presence of the mink, either being absent or having a lower abundance where mink are present.