Acta Zoologica Cracoviensia, 38(3) 1995

Issue:

VOL 38(3) 1995

Keywords:

Sterna vittata, biology, nests, eggs, breeding success, diet, Antarctica

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Distribution, abundance and biology of the Antarctic Tern Sterna vittata Gmelin, 1789 on King George Island (South Shetland Islands)

• Bolesław JABŁOŃSKI

Abstract:

A total of 3518 pairs of Antarctic Terns nested on King George I in the 1980/81 season. In the region of Admiralty Bay the numbers ranged from 652 to 1828 pairs (7.2-20.1 pairs per 1 km of coastline). Most pairs nested on rock-rubble heaps void of vegetation and on moraines. On the average 1.45 eggs, 0.46 newly hatched chick and0.22 young bird leaving the colony fell to one pair. Mean dimensions calculated from 498 eggs were 44.8 x 33.5 mm. Single eggs and the first ones of two-egg clutches were longer. The first chicks grew faster. The diet of adult and young birds consisted of Euphausia, Amphipoda and Pisces. Their proportions in the food of the young changed with age. The total consumption of krill by Antarctic Terns in the region of Admiralty Bay was 4.69-4.93 tons in the 1980/81 season, which makes 0.60-0.78% of its biomass. A relatively small amount of faeces excreted on land and the considerable scattering of nests cause that the role of Antarctic Terns in the formation of ornithogenic soils is of minor significance, whereas the presence of their colonies may be important to the development of associations of nitrophilous lichens.