Abstract

IBARRA, José Tomás; SCHUTTLER, Elke; MCGEHEE, Steven  and  ROZZI, Ricardo. CLUTCH SIZE, NESTING SITES, AND BREEDING SUCCESS OF THE UPLAND GOOSE (CHLOEPHAGA PICTA GMELIN, 1789) IN THE CAPE HORN BIOSPHERE RESERVE, CHILE. Anales Instituto Patagonia (Chile) [online]. 2010, vol.38, n.1, pp. 73-82. ISSN 0718-686X.  doi: 10.4067/S0718-686X2010000100004.

Studies on the biology of the Upland Goose (Chloephaga picta) in Chilean Sub-Antarctic ecosystems are scarce and basically constitute anecdotic records of the species. With the aim to broaden this knowledge, we studied its breeding biology in terms of clutch size, nesting sites and breeding success as a function of habitat variables on Navarino Island (54-55ºS), Cape Horn Biosphere Reserve(CHBR), Chile. We monitored 79 nests in coastal habitats during 54 days of breeding activity in the nesting season of 2005/2006 and 59 days in 2006/2007. Clutch size was 6.1 ± 1.2 eggs. Nests were preferably built on coastal sites with low slope (0-10º). The dominant breeding habitat was shrubland (70.5%) dominated by Chiliotrichum diffussum (30.8%) and Berberis buxifolia (24.4%). Pebbles were the most common element on the nesting sites (50.1%). The overhead nest concealment was low (0-25%) in 82.1% of the nests, andlateralcoverage wasintermediate(25-50%) in 29.5%. 39.7% of the nests were built in habitats with relatively high vegetation cover (>40%). In total, 36.7% of the clutches hatched (successful following the traditional method) and 57,0% were predated. Measured habitat variables did not explain success or failure of the nests. The nest survival probability was 20,0% (Mayfield method). The two calculated values are lower than those reported in other geese species (>60%) and also than values (61-75%) reported for this species in Falkland-Malvinas Islands (300 km from Navarino Island). This study shows the need of understanding more aspects of the biology and conservation of C. picta in the CHBR, in particular when considering the environmental changes (invasive species, tourism development, climate change, etc) currently going on in the Sub-Antarctic systems.

Keywords : breeding biology; Chloephaga picta; clutch size; Mayfield; Navarino Island; nesting success; predation; Sub-Antarctic.