Summer Birds of the Pack Ice in the Weddell Sea, Antarctica

Abstract

SEVERE pack ice conditions have greatly limited scientific investigations in the Weddell Sea, that expanse of water east of the Antarctic Peninsula. Since the sea's discovery by the British navigator James. Weddell in 1823, it has presented a formidable obstacle to explorers and scientists alike. As participants in the 1968 International Weddell Sea Oceanographic Expedition (IWSOE), we were given an unusual opportunity to obtain information on the wildlife species frequenting this remote part of the world. Our investigations were carried out from aboard the USCGC 'Glacier,' an icebreaker capable of operating continuously in heavy pack ice, which enabled us to reach parts of the Weddell Sea never before visited by man. This venture was undertaken and financed by the United States Antarctic Research Program (USARP) of the National Science Foundation. Although our primary concern was a population study of antarctic seals, a considerable amount of time was also spent observing birds. This paper reports the occurrence, distribution, and relative density of the bird species we encountered in pack ice of the Weddell Sea during the 1968 austral summer. The information was obtained during 95 hours of census taking between 30 January and 15 March 1968. Counts were made on 35 of the expedition's 44-day cruise between 62?09' and 75?28' S and 38?07' and 60?09' W (Figure 1). Sladen and Friedman (1961), among others, revealed that considerable attention has already been given various aspects of antarctic ornithology, but Voous (1965) emphasized that details of the pelagic distribution, specific behavioral differences, and the seasonal vicissitudes of most species are still incompletely known. Szijj (1967) considered the Antarctic Convergence as the transition area between bird faunas of the southern ocean, but with much blending and mixing between truly antarctic and subantarctic species obscuring this division. According to Voous (1965), at least 33 species of birds frequent antarctic waters during the summer. Of these 17 nest on the antarctic continent (Sladen and Friedman, 1961). Little has been reported on the avifauna of the Weddell Sea, especially in areas of pack ice. Clarke (1907) summarized the findings of biologists aboard the 'Scotia' during the Scottish National Antarctic Expeditions of 1903 and 1904, and Novatti (1962) discussed the pelagic distribution of 24 species of birds in the Weddell Sea during the summers of 1955-56