Ruddy-headed Goose Chloephaga rubidiceps: Former plague and present protected species on the edge of extinction

Abstract

The Ruddy-headed Goose Chloephaga rubidiceps has two separate and genetically distinct populations, one sedentary that inhabits the Malvinas/Falklands Islands and another migratory, which inhabits continental southern South America. New information suggests that these populations should be considered as different evolutionarily significant units. The latter population breeds in Austral Patagonia (Argentina and Chile) and overwinters in Central Argentina. It was a very common species in Austral Magellanic steppe grasslands before 1931, when it was declared an agricultural pest by the Argentinian government, together with other sheldgeese species. Since then, the continental Ruddy-headed Goose population has declined becoming one of the scarcest species in Austral Magellanic steppe. Nowadays, its population is categorised as critically endangered in Argentina and endangered in Chile. We present data from six road censuses conducted in the breeding areas of Santa Cruz and Tierra del Fuego provinces, Argentina, during 2013-2014 and 2014-2015 (>4600 km, 70 days) and review population trends of the Ruddy-headed Goose since the early 1900s. We counted a maximum of 19 individuals in Santa Cruz and 49 in Tierra del Fuego throughout the breeding season. A literature review indicates that during the last 40 years the size of continental population of Ruddy-headed Goose has been < 800 individuals, approximately 10% of the estimated population in the 1900s. This decline matches the period following the application of control techniques and the introduction of exotic predator species in the breeding grounds of Tierra del Fuego. We review and discuss formerly proposed conservation actions that may have a positive and rapid effect on sheldgoose numbers recovery. We suggest that the continental population of Ruddy-headed Goose should on a precautionary basis be treated as a critically endangered population until genetic studies determine whether we are in the presence of a new 'Critically Endangered' species.