The Breeding Status of Adelie penguins and other birds on the coast of George V Land, Antarctica

The following are excerpts from Ensor and Bassett (1987). A census by counts and estimates of Adelie penguin chicks on the George V Land coast of Antarctica between Commonwealth Bay and Buchanan Bay was undertaken during January 1982. Sections of colonies were photographed for comparison with photographs taken in 1913 during the Australasian Antarctic Expedition; positions and sizes of sub-colonies appeared unchanged after an interval of 68 years. Observations on the distribution of breeding Antarctic fulmars, Cape petrels, Snow petrels, Wilson's storm-petrels and South polar skuas are presented. This report describes the breeding status of seabirds, particularly Adelie penguins, on the George V Land coast of Antarctica between Commonwealth Bay (67 degrees S, 142.5 degrees E) and Buchanan Bay 67.1166 degrees S, 144.6666 E). The area was visited in January 1982 during the Mawson anniversary expedition of the Oceanic Research Foundation (ORF) on the schooner Dick Smith Explorer. The observations on the breeding of seabirds were conducted as a contribution to the International Survey of Antarctic Seabirds (ISAS) designed to investigate the abundance and distribution of seabirds in the Southern Ocean ecosystem. Of particular interest to this program is the the population status of Adelie penguins Pygoscelis adeliae. The George V Land coast has seldom been visited. The main expeditions to the area have been the 1911-13 Australasian Antarctic Expedition (AAE) and the 1929-31 British, Australian and New Zealand Antarctic Research Expedition (BANZARE). Falla (1937) summarised the biological observations made during these expeditions, including estimates of the numbers of Adelie penguins breeding in the Cape Denison area (67 degrees S, 142.6666 degrees E). The Australian National Antarctic Research Expeditions and Expeditions Polaires Francaises have also made visits. The present observations provide a recent estimate of the breeding population of Adelie penguins in the area. Since the authors' visit to the colonies was late in the breeding season, estimates of numbers were restricted to chicks. The number of chicks gives an approximation of the number of pairs of penguins breeding but due to annual variations in breeding success, these estimates are not as reliable as the direct counts of occupied nests that can be made during the incubation period. The 1981-82 ORF expedition was based at Cape Denison between 11 and 30 January 1982 where a census of Adelie penguin chicks and observations on the breeding of other birds was conducted. A camp was established on the Mackellar Islands (66.9666 degrees S, 142.65 degrees E) from 12 to 14 January to enable a census of penguin chicks to be made. On 30 January the expedition departed Cape Denison towards the Mertz Glacier tongue (154.3333 degrees E). The cruise track of the vessel followed approximately the outer limit of islets of the Way Archipelago (143.6666 degrees E) and passed close to Moyes Islands (143.85 degrees E) and Hodgeman Islands (144.25 degrees E). Brief visits were made to two islets in the Way Archipelago, Stillwell Island (143.8 degrees E) and an unnamed islet near Garnet Point (143.7666 degrees E). En route to the Mertz Glacier, a planned landing at Cape Hunter (66.95 degrees S, 142.3333 degrees E) to investigate the breeding population of seabirds including a large colony of Antarctic petrels Thalassoica antarctica (Falla 1937), had to be abandoned due to the onset of high winds. Adelie Penguin, Pygoscelis adeliae Locations of Adelie penguin colonies and counts and estimates of the numbers of chicks in each colony are given in a spreadsheet available at the url below. The total numbers of Adelie penguin chicks on the coast between Cape Denison and Buchanan Bay was 55,242. At Cape Denison, on the Mackellar Islets and on Stillwell Island, direct counts of chicks were made. Counts were replicated until a 5% accuracy was achieved. To aid the counting, the distribution of guano (which approximates to the extent of the sub-colonies) was mapped. On 12 January at Cape Denison, the first day of the author's counts, chicks were not yet in creches and were still protected by adults at their nest sites. It was possible therefore to count the number of occupied nests, the number of single chicks and pairs of chicks. These counts were obtained for 14 sub-colonies and in 297 nests 413 chicks were recorded. The 4898 chicks counted in the whole of the Cape Denison colony should therefore represent 4898 x 297/413 = 5322 nests at this stage of the breeding season. The original number of pairs of penguins that bred at Cape Denison in the 1981-82 season was greater than 3522 by an unknown number. A more accurate estimate of the actual number of pairs of penguins that bred at Cape Denison in the 1981-82 season could not be made because the authors have no knowledge of breeding failure prior to their visit. Previous estimates for Cape Denison were over 5000 pairs in January 1931 (Falla 1937) and 2000 pairs in January 1974 (Horne 1983). The authors have not adjusted the number of breeding pairs at colonies other than Cape Denison because it appears there is a difference in the breeding success between colonies in this area. Circumstantial evidence for this was the retarded development of chicks observed at Cape Denison. On 12 January chicks were still protected by adults at their nest sites, while the following day on the Mackellar Islets 7 km away, large creches of chicks from previous seasons were far more abundant than at any of the other colonies visited, suggesting a higher mortality of chicks at this colony. A probable factor inducing the retardation of breeding and higher chick mortality at Cape Denison is the severe weather characteristic of this locality (Mawson 1915). The strong katabatic winds that prevail at Cape Denison lose much of their force before reaching the offshore islands. Photographs were taken at Cape Denison and on Greater Mackellar Islet and compared with those taken in the 1912-13 breeding season during the AAE (Falla 1937). The relative positions and sizes of the sub-colonies were very similar after an interval of 68 years. Unfortunately the authors did not have the opportunity to take a photograph to match that taken by Falla on Lesser Mackellar Islet in 1931, but comparison with the authors' sketch maps of the sub-colonies indicates that the sizes and positions of the sub-colonies are similar. Although the authors have no knowledge of the numbers of penguins that bred in other parts of these colonies in the 1912-13 and 1929-31 breeding seasons, the similarity of the sizes and positions of the sub-colonies suggests that the current breeding population at Cape Denison and on the Mackellar Islets is comparable to that present in 1911-13 and 1929-31. This implies that the breeding population of penguins on this part of the Antarctic coast has been relatively stable over some 70 years. On this basis it is likely that the previous estimates of numbers of breeding penguins on the Mackellar Islets, 100,000 pairs in the 1913-14 season and 200,000 pairs in 1930-31 (Falla 1937), were too high, as the authors' count was 27,130 chicks. During the authors' visit to the unnamed islet in the Way Archipelago there was insufficient time to conduct a census of chicks and so photographs were taken from which chicks were subsequently counted. Counts and estimates of chicks in breeding colonies at Cape Gray (66.85 degrees S, 143.3666 degrees E), Moyes Islands, Hodgeman Islands and islets of the Way Archipelago (apart from the two on which the authors landed) were conducted from the vessel and the colonies were mapped in detail. Chicks on islets near to the vessel were counted individually and estimates of chick numbers were made only when the colonies were too distant and individual chicks could not be counted. The accuracy of counts and estimates of chick numbers conducted from the vessel depended on the vessel's distance from the colonies, the terrain and aspect of the breeding areas and visibility. Sun glare and obstruction of view by other islets and icebergs sometimes affected visibility. Use of binoculars was restricted by vibrations of the vessel. Therefore the counts and estimates of number of chicks conducted from the vessel, during which only the colonies in view were considered, underestimated the actual number of chicks, since substantial proportions of some colonies were probably hidden from view. Cape Pigeon Rocks, for example, most probably have relatively large numbers of penguins nesting on their landward facing slopes. This is evidenced by well-defined penguin tracks leading up the snow slopes on the seaward facing aspect. Some islets were several miles from the vessel and although the identification of penguins breeding on them was not always possible, we assumed all were Adelie penguins. Photographs of the islets were taken for comparison with the author's field notes and a selection of these have been lodged with the Australian Antarctic Division. No penguins were observed breeding on the Laseron Islands (66.9833 degrees S, 142.8 degrees E), Blair Islands (66.8333 degrees S, 143.15 degrees E), Fletcher Island (66.8833 degrees S, 143.0833 degrees E), Hannam Islands (66.9166 degrees S, 142.95 degrees E) or on the Close Islands (67.05 degrees S, 144.55 degrees E). There appears to be a medium-sized colony of Adelie penguins at Cape Hunter, but weather conditions prevented getting close enough to make an estimate of the number of chicks present. Antarctic Fulmar, Fulmarus glacialoides About 190 Antarctic fulmar nests with chicks were found on Stillwell Island. Fulmars on nests were seen from the vessel on two other islands in the Way Archipelago. These islands had about 75 and 20 nests. Cape Petrel, Daption capense A single Cape petrel nest, containing one chick, was found on Stillwell Island. Snow Petrel, Pagodroma nivea Thirty occupied nests were found at Cape Denison, 4 on the Mackellar Islets and 10 on Stillwell Island. More nests certainly would have been present at Cape Denison, but nest sites are restricted on the islands. Wilson's Storm-Petrel, Oceanites oceanicus During a brief search at Cape Denison, 5 nests of Wilson's storm-petrels were located. Apparently suitable breeding habitat occurs over large areas at Cape Denison and many more nests probably exist. On Greater Mackellar Islet, 4 nests were found and on Lesser Mackellar Islet the authors found 7. More nests probably exist on each of these islets although suitable habitat is restricted. No nests were found on Stillwell Island, but many storm-petrels were seen flying about the island in the evening. Antarctic Prion Pachyptila desolata Antarctic prions were found nesting at Cape Denison in 1913 during the AAE, in the vicinity of John O'Groats near the eastern barrier. A pair was shot on 3 December and the specimens (no. 22083 and 22084) are now in the Australian museum, Sydney. One member of a second pair was shot on 10 December, but the specimen was lost in the water. On 11 December, a prion was found in a crevice under a rock, with bones and an egg, evidently from a previous season. On 16 December, two more eggs were found (Falla 1937). This is the only record of Antarctic prions breeding at the Antarctic continent, apart from the Peninsula region. During the evacuation of an ANARE party in February 1978, a small bird was found tangled in the radio aerial during dis-assembly. It was badly injured and was killed to prevent further suffering. It was placed under a rock. Early in 1981, it was retrieved and identified as an Antarctic prion (G.W. Johnstone, pers. comm.). The radio aerials were on the hill south of the Mertz memorial cross. This is the only record of an Antarctic prion at Cape Denison since the AAE. The authors spent several evenings watching for prions in the vicinity by John O'Groats, and searched for nests but saw no birds and found no nests. The status of Antarctic prions at Cape Denison remains enigmatic. South Polar Skua, Catharacta maccormicki South polar skuas were found breeding at all areas visited. Nests at Cape Denison (4), Greater Mackellar Islet (3), Lesser Mackellar Islet (3), Stillwell Island (3) and the unamed islet in the Way Archipelago (3) each contained one chick. Two of the birds breeding at Cape Denison and on on Lesser Mackellar Islet were banded. Two of these had Paris Museum bands and had been banded by French biologists at Dumont d'Urville 150 km to the west. The other bird was timid and its band number could not be read. The dataset consists of a spreadsheet of chick numbers by date and location, several locality maps and comparative photos. The fields in this dataset are: Location Date Chick Numbers