Population counts and monitoring of the breeding cycle of Adelie penguins (Pygoscelis adeliae) throughout an entire breeding season at Cape Royds

The breeding colony at Cape Royds was kept under daily observations during an entire breeding season before birds started arriving (only 17 present when observations started) until all birds had departed for sea. Two main studies were conducted; population counts and the breeding cycle. Total population counts were made of the entire rookery at least every two days (daily during the occupation period and at the end of the season). The rookery was divisible into 15 colonies and 8 of these were further treated in greater detail.

The data collected includes: the total number of adults, the number of nests occupied, the number of nests with both mates present, the number of nests with eggs or chicks and the number of chicks present. Accurate chick counts were not possible until the beginning of the creche stage. The data may be useful for estimating the size of other rookeries from short term visits. Daily observations were carried out on 50 individually marked pairs of penguins and supplemented by observation on an additional 75 marked nests. Eggs and chicks were individually marked. The information recorded includes dates of arrival, occupation of nests, pair formation, laying dates and clutch size, incubation period, parental routine, growth of young, losses of eggs and chicks, creche formation and departure of chicks for sea. The nests observed included those of both early and late laying birds as well as nests inside colonies and those on the edges or in isolated positions, and information has been collected on the comparative breeding success of these different groups. In the majority of cases the causes of egg losses or chick mortality could be determined. Many incidental observations on the biology of Adelie penguins were recorded. A large scale map was prepared showing the distribution of the colonies within the adelie rookery and this was supplemented by still photography.