Harteman Wildfowl, presented by Jan Harteman
This species breeds on northern Tierra del Fuego Island (Chile and Argentina) and southern Santa Cruz, wintering in southern Buenos Aires, Argentina; there is also a virtually sedentary population on the Falkland Islands (Malvinas) (del Hoyo et al. 1992).
The continental population of the Ruddy-headed Goose is migratory and is in imminent danger of extinction because of the small size of its population, its restricted area of distribution, and the numerous threats which it faces in its breeding grounds in the continental area of the Magallenes region (Chile), in the north of the Tierra de Fuego (Argentina and Chile) and in the wintering grounds in the South of Buenos Aires province (Argentina). Therefore the MoU aims to safeguard the mainland population of this species, which is in serious danger of extinction.
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern (IUCN, 2012).
The species has a large global population estimated to be 43,000-82,000 individuals (Wetlands International 2006). The population on mainland South America has decreased considerably, with simultaneous censuses in southern Chile and Argentina recording 312 individuals in 1998 (Y. A. Vilina in litt. 1998). Although abundant on Tierra del Fuego in the 1950s, a census in the 1973 breeding season yielded only 30 birds (del Hoyo et al. 1992). However, it is fairly common in the Falklands with 14,000-27,000 pairs estimated in surveys between 1983 and 1992 (Woods and Woods 1997).
The species is found in open country, frequenting coastal grassland and meadows, often with Upland Goose C. picta and Ashy-headed Goose C. poliocephala (Argentina only). It feeds on roots, leaves, stems and seed-heads of grasses and sedges in natural grasslands, pastures and agricultural lands (del Hoyo et al. 1992). It nests from late September to early November in the Falklands, with nests recorded until January on Tierra del Fuego (Woods and Woods 1997, Chebez 1994).
The Argentinean federal government declared C. rubidiceps a pest in the 1960s, claiming it fed on wheat and corn crops, and competed with sheep and cattle stocks for grassland resources in Buenos Aires (Chebez 1994). Although there is no evidence to support the latter and its numbers are too few to seriously effect the former, this promoted the active destruction of the species and persecution at its wintering grounds is certainly a factor contributing to its decline. However, this is not true on the Falklands, where 100,000 were killed in the period 1905-1912 and fair numbers are still killed each year, but the mobility of the species apparently renders efforts to reduce its numbers ineffective (del Hoyo et al. 1992). It was also removed from the list of pest species (Schedule I of the 1964 Wild Animals and Bird Protection Ordinance) on the Falklands in 1985 (Woods and Woods 1997). The introduction of Patagonian Grey Fox Dusicyon griseus as a control for the European Rabbit Oryctolagus cuniculus on Tierra del Fuego is perhaps also a contributory factor in the species's decline (Chebez 1994). It is possible that the smaller sized C. rubidiceps is at some disadvantage in interspecific encounters with the larger and perhaps more aggressive C. picta leading to the displacement of C. rubidiceps from foraging and nesting sites.
Above: adult Ruddy-headed goose.
Above: adult Ruddy-headed goose