HABITAT USE AND BREEDING DISTRIBUTION OF MAGELLANIC PENGUINS IN NORTHERN SAN JORGE GULF, PATAGONIA, ARGENTINA

Abstract

Abstract We evaluated distribution and size of Magellanic Penguin (Spheniscus magellanicus) colonies in northern San Jorge Gulf, Argentina, characterizing nesting habitat at 14 islands with colonies (IC) and 28 islands without nesting penguins (INC). Digital analysis of a Landsat TM satellite image and field measurements were used to assess vegetation and substrate. The 14 breeding colonies ranged in size from 13 to 96,300 nests, and number of breeding pairs was estimated at 218,460. Colonies were only located on islands. Digital analysis of the satellite image showed that the proportion of area with shrub–steppe vegetation was significantly higher at IC than at INC (38.6 vs. 4.9%), whereas percentage of rocky substrate was lower at IC (33.6 vs. 64.8%). Percentage of vegetation cover was positively correlated with island area and with number of breeding pairs. Most nests (98.6%) were located under bushes, whereas the rest were burrows dug into the substrate. Mean size of bushes used for nesting was higher...