Aspectos poblacionales, uso del hábitat y dieta de la Guayata Oressochen melanopterus (Aves: Anatidae) durante la invernada en el valle de Calingasta, San Juan, Argentina

The breeding distribution of the Guayata O. melanopterus , includes mountain ranges from Peru to Argentina and Chile, at altitudes of more than 3000 masl. During the non-breeding season part of its population migrates to lower regions (below 2000 masl), at least in the southern part of its distribution. In Argentina, its conservation status has been established as vulnerable, due to the increased interactions with human extractive activities. During July 2016, we estimated the population size, described the use of the environments and the diet of the Guayata that were wintering in Calingasta valley, San Juan province, Argentina. We counted a maximum of 894 individuals (range 2-390), noting that a high proportion of the flocks was composed of two individuals (35.7%). The population for Calingasta valley was estimated at 3500 (± 2000) individuals. The Guayata were significantly associated with the valley environments occupied by cultivated low-growing pastures located close to the water. The diet was exclusively herbivorous, comprising only seven species of plants belonging to two main groups: dicotyledons (70.7%) and grasses (22.6%). The bestre presented species were legumes, white clover Trifolium repens and alfalfa Medicago sativa (44.3% and 26.1%, respectively) followed by a grass, namely at Avena sativa (16.0%), all of which are important for the local agriculture. Due to its vulnerable conservation status, the possible conflict between the Guayata and agriculture requires attention to improve the protection of this species in the Calingasta valley.