Diet diversity and prey selection of Chubut Steamerducks (Tachyeres leucocephalus)

AGUERO, LAURA; GARCIA BORBOROGLU, P.; ESLER, DANIEL

Cuzco

Congreso; IX Neotropical Ornithological Congress; 2011

Sociedad de Ornitologia Neotropical

Chubut Steamer-Duck is a flightless anatid endemic of the Central Patagonia marine coast, Argentina. According to the IUCN Red List of Threatened Species, the species was included under the near threatened category based on the lack of information. The existing information on this species ecology is extremely limited and there is not even precise data about its trophic ecology.We analyzed diet diversity and the degree of prey selection (donde y cuando) at Golfo San Jorge Gulf, Argentina, from 200X-200x. During breeding season, 46 faeces were collected along 15 territories. Samples were washed in two sieves (1 and 0.5 mm mesh) under a jet of water. Fragments that were resistant to digestion and diagnostic of invertebrate taxa were identified under a stereoscopic microscope at 10 X 40 magnification. Identification was made to the lowest taxonomic level possible based on preserved material and specific taxonomic keys. Diet diversity was calculated using Levin’s standardized index (Bsta) and prey selection was determined using Jacobs’ index. A total of 13 food components/species? were identified: seven mollusks, two crustaceans, polychaetes and unidentified organic matter. Crustaceans comprised 93.5% of the Steamerducks’ diet (n?=43 faeces) followed by mollusks 69.6% (n=32 faeces) and Nereidiidae 54.35% (n=25 faeces). Taking into account the major food category considered, the Steamerducks’ diet diversity was relatively low (Bsta=0.28). They significantly select Cytograpsus sp. (P