Chubut Steamer-Duck (Tachyeres leucocephalus): Breeding Habitat Requirements and Selection in Patagonia, Argentina.

AGÜERO, M.LAURA; GARCÍA BORBOROGLU, PABLO; ESLER, DAN

Quebec, Canada

Congreso; Third North American Seaduck Conference.; 2008

Environment Canada (Canadian Wildlife Service and Science & Technology, Québec Region) and Regroupement Québec Oiseaux

Chubut Steamer-Duck is a flightless anatid endemic of the Central Patagonia marine coast, Argentina. IUCN listed this species as near threatened based on its restricted distribution range and low population size. Chubut Steamer-Duck’s breeding habitat requirements and selection were studied along the Chubut Province marine coast, Argentina, between 2004 and 2006. The study area covered a 341 km coastal sector and included 32 islands, encompassing its main breeding area. The general habitat was characterized, and to evaluate the microhabitat selection, 10 habitat variables were quantified at 169 nests and at 166 random points at northern San Jorge Gulf. In this sector, nests were only located on small and medium-sized islands and islets (9.87 ± 12.92 ha; range=0.5-54.4 ha) and relatively close to mainland (1.15 ± 1.14 km; range= 0.01–5.6 km). Nesting areas were adjacent to the coastline, located within sheltered bays and inlets with shallow protected waters. Multivariate analysis to compare nest and random-points characteristics showed that Chubut Steamer-Duck selected sites with higher shrub-type vegetation cover (63.91 ± 30.14%), flat surfaces (3.74 ± 1.91°) with high proportion of silt-clay (60.18 ± 37.49), but low percentages of rock (4.2 ± 13.54). Nests were built on the ground, mainly under bushes, and nesting material consisted mainly on downfeathers, branches and mollusk shells. The nests’ mean external and internal diameters were 33.3 and 19.8 cm, respectively, whereas mean nest depth and external height were 8.8 and 4.1 cm, respectively. General habitat requirements seem to be related mainly to the proximity to adequate water bodies for adults and chicks to forage and a safer place to raise ducklings, while nest-site selection may be associated with concealment from aerial predators and protection from weather. The information presented will allow better implementation of conservation measures for this species and its habitats.