Counts of Adélie penguin populations are most conveniently and most often undertaken at breeding sites during the breeding season. The objective of this paper is to identify and describe the aspects of Adélie penguin population structure, dynamics and demography that are relevant to the interpretation of counts made at breeding sites and the estimation of overall population abundance derived from such counts. To appreciate what counts conducted at different times within a breeding season represent, it is important to understand the population dynamics of the different components of the population throughout the breeding season. The conceptual model described here is specifically based on data obtained from the Adélie penguin population at Béchervaise Island, East Antarctica. While the various life stages described here are also likely to represent other Adélie penguin populations, details in the proportion of each category either at the breeding site or at sea may potentially differ.