Little is known about bird ecology in sub-Antarctic ecosystems of the Cape Horn Reserve (CHBR), Chile. We examined the role of altitude, seashore distance, lake size, season, and vegetation cover in affecting bird diversity and abundance on Navarino Island (54-55°S, 67°W) in the CHBR. We determined avian community composition, species richness and relative abundance for wetlands and their adjacent habitats on a seasonal basis. A total of 56 species belonging to 10 orders and 25 families were recorded, and significant seasonal changes for bird species (P = 0,001) and abundance (P<0,01) were observed, with 33,9% residents, 48,2% winter migrants, and 17,9% with unknown migratory status. The distance of wetlands from the coastline was the main predictor variable for annual species richness (P<0,01) and total avian abundance (P<0,05). Wetlands far from the seashore and at higher altitudes had lower diversity and abundance, although the change in elevation was relatively slight (< 300 m). These data show the seasonal patterns and dynamics, as well as the major underlying mechanisms, for birds of wetlands and adjacent habitats in the CHBR.