In conjunction with aerial photographs of the colonies ground truth counts were made since the 1983-1984 season at the Ross Island colonies. The number of occupied nests, nests with eggs, nests with both adults present and total penguins at the colony were censused to be able to check for accuracy of the counts from aerial photographs and to assess the breeding status and condition of the birds for that year. Since 1990, ground counts of chicks at each rookey were conducted in late January to measure breeding success (number of chicks/breeding pair). Approximately 100 chicks were selected randomly at each site and they had their weight and flipper length measured to calculate a chick condition index which is comparable between years and between the rookeries.
Wilson, P.R. Ainley, D.G. Nur, N. Jacobs, S.S. Barton, K.J. Ballard, G. Comisco, J.C. (2001). Adélie penguin population change in the Pacific sector of Antarctica: relation to sea-ice extent and the Antarctic Circumpolar Current. Marine ecology progress series 213: 301-309.
Greenfield, L.G. Wilson, K.J. (1991). Adélie penguin colony estimations from aerial photography and ground counts. Polar record 27(161): 129-130.