Methodology:

Adelie penguin colonies, predetermined as distinct groups of breeding pairs, were selected and surveyed using ground counts starting in the 1978 to 1997 season. In total, nine Adelie colonies were surveyed annually. Optimal count dates were determined by monitoring 100 Adelie nests in one, specifically-monitored colony for the species used to establish annual breeding chronology (CEMP Standard Method A9).

Monitoring comprised of counts of occupied nests and incubating nests for Adelie penguins. Nests were categorised as "incubating" (at least one egg present) and "occupied" (no eggs observed) either through manual nest marking, or observations from the colony edge using a tally counter. This was carried out one week after peak egg-laying (CEMP Standard Method A3A). Subsequently, chick counts were also carried out by manual nest marking, or if possible by observations from the colony edge. Lastly, fledgling counts were completed when all chicks had entered creche (CEMP Standard Method A6C). Counts were always individually repeated three times on the same day, until within 10 percent of each other. From the 2006/2007 season onwards, hand-held GPS devices were also used to provide specific coordinates of each surveyed colony.

An annual index of breeding population size is then calculated by determining the mean values of the number of occupied nests and incubating nests for several aggregated colonies. Breeding success can be calculated by taking the annual number of creched chicks prior to fledging, divided by the total number of breeding pairs.

Data quality:

Standard CCAMLR (CEMP) monitoring methods were implemented in 1996. Prior to this date, counting methods and timing of counts may have varied, which should be considered when comparing counts and calculating inter-annual trends from previous seasons.

For some seasons, only information on specific parameters was possible to obtain (when the base would open late/shut early). In some years, certain data pertaining to chick counts was not possible to obtain. For NA values in the column titled "Total number of nests without eggs", which is carried out mid-season, some, if not all failed nests are abandoned by the time of the survey. Their stones are then stolen by other nesting birds, and the nests are no longer visible to field assistants. Abnormalities or the lack of data collected for other reasons is explained in the comments alongside that season's data.

More details on the counts can be provided upon request to the Polar Data Centre.

GPS coordinates are of colonies that were measured with GPS devices. There are colonies that are no longer present or monitored that do not have GPS coordinates.