This study aims to investigate the factors regulating population size and colony distribution of Adelie penguins (Pygoscelis adeliae) at Cape Hallett. Data was collected on Adelie penguin reproductive effort and chick condition including total number of adults, number of breeding pairs, number of active nests, number of territories, number of unknown, nests with 1 or 2 eggs, nests with 1 or 2 ... chicks and the number of creche chicks. Satellite transmitters and time depth recorders were used to track individual penguins at sea to determine their foraging areas and strategies during the breeding season. Regurgitated food samples were collected for analysis. Chicks were selected randomly and were weighed and had their flipper length measured to calculate a chick condition index which is comparable between years and between the rookeries. Feeding frequency and reproductive effort was determined from chick feeding observations.