This study aims to investigate the factors regulating population size and colony distribution of Adelie penguins (Pygoscelis adeliae) at three colonies on Ross Island (Cape Royds, Bird and Crozier) and when logistics allowed Beaufort Island through studying the importance of key resources (nesting space and food) and the way they are allocated by behavioural traits (philopatry, immigration and ... emigrations). A range of techniques was used to collect data. A sub-colony was fenced off and an automated weighbridge and data logger was installed at each colony. Several pairs of breeding birds were implanted with a passively interrogated transponder. When a bird steps on the weighbridge, the data logger would record direction of travel, weight and tag number, if a tag was present. These data were used to determine foraging effort (feeding trip duration and food load size). The productivity and chick condition index was measured in birds in the enclosure and those in an undisturbed colony to check for negative effects of the weighbridge. The stomach contents of Adelie penguin adults and chicks were examined for food prey species over time and between colonies. The diet quality was compared by analysing stable isotope (C and N) ratios in samples collected from dead chicks (protein rich, lipid poor tissue). GIS and satellite images were used to determine the effects of sea ice conditions on colony success (availability of food, breeding success, etc). To measure the effect of sea ice extent and availability of food on breeding success, 50 chicks/week/colony were randomly caught, weighed and flipper length measured to calculate a chick condition index as an indication of food availability during chick rearing stage. These data were comparable between years and colonies. To measure the immigration/emigration and philopatry behaviour role in colony size and distribution, chicks were banded at each colony (up to 1000 chicks/colony/season). In following seasons, searches were made for banded penguins at all colonies to estimate age specific fecundity and survival rates, age of first breeding and to measure immigration/emigration rates for each of the study colonies. The role of natal philopatry in the structure of colony formation was assessed by measuring genetic homogeneity among and within the colonies on Ross Island using mitochondrial DNA analysis. Radio telemetry, satellite tracking and time depth recorders were used to track individual penguins at sea to determine their foraging behaviour. To track post breeding migration, winter migration and over wintering feeding grounds, archival tags that determine geo-location were deployed on birds from Cape Royds and Crozier. Birds were recaptured the following season and data downloaded.