Population size and breeding success of chinstrap penguins on Signy Island from 1978 to 2020.

Chinstrap penguin colonies, predetermined as distinct groups of breeding pairs, were selected, and surveyed using ground counts starting in the 1978-1979 season. In total, eleven chinstrap colonies were surveyed annually. Optimal count dates were determined by monitoring 100 chinstrap 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 chinstrap 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 when possible by observing 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.