Survey of marine birds and mammals of the South Sandwich Islands

Abstract

During January and February 1997, two separate surveys of the birds and seals of the South Sandwich Islands archipelago were made, with further data obtained from the northern islands during February 1998. Together, these surveys provide the most recent and accurate estimates of breeding populations of most species, their distributions, and their habitat. Observations were made (1) from a small vessel operating close inshore, which surveyed approximately 92% of the archipelago's coastline, in addition to making shore counts at selected locations; (2) during a six-week shorebased field camp on Candlemas Island; and (3) opportunistically during helicopter-supported landings and airborne operations over all islands in the archipelago. The surveys recorded 16 species of breeding birds, including the first confirmation of breeding by black-bellied storm petrels (Fregetta tropica) and Antarctic terns (Sterna vittata), the second record of incubating king penguins (Aptenodytes patagonicus), and the location of many previously unrecorded seabird breeding sites. The population of chinstrap penguins (Pygoscelis antarctica), at approximately 1.5 x 10 pairs is considerably less than the estimate of 5 x 10 pairs currently in use, and represents about 30% of the world population. Populations of chinstrap penguins, Antarctic fulmars (Fulmarus glacialoides), cape petrels (Daption capense), and snow petrels (Pagodroma nivea) in the South Sandwich Islands are of global significance. Five species of seals were recorded. At the time of the surveys, only Antarctic fur seals (Arctocephalus gazella) were confirmed to be breeding, and several new breeding sites were located. Pup numbers showed a small increase compared with the few earlier records, but the population has not undergone the large increases seen on South Georgia and at sites in the maritime Antarctic. The other four species recorded are considered highly likely to breed either within the archipelago or amongst pack ice that seasonally surrounds the islands.

Limited genetic differentiation among chinstrap penguin (Pygoscelis antarctica) colonies in the Scotia Arc and Western Antarctic Peninsula

“…data), and the total populations of chinstrap penguins in South Orkney Islands are estimated at 405,600 pairs (Trivelpiece and Trivelpiece 2013). Thus, the total breeding population of chinstrap penguins at these two sites and regions is smaller than those found at Admiralty Bay, King George Island (around 2000 pairs; Sander et al 2007;Trivelpiece et al 2011) in the South Shetland Islands (986,440 pairs; Trivelpiece and Trivelpiece 2013) and Thule Island (45,000 pairs; Convey et al 1997), in the South Sandwich Islands (1,285,000 pairs; (Trivelpiece and Trivelpiece 2013). The low but significant level of inbreeding signatures found at Orne Harbour and Signy Island thus may be a function of their relatively smaller population sizes.…”

Responses of seabirds, in particular prions (Pachyptila sp.), to small-scale processes in the Antarctic Polar Front

“…Of the potential breeding locations, only Bouvet Island is relatively close at 7700 km, but this location supports only marginal populations of broad-billed prion and Black-bellied Stormpetrel and none of the other major species in this study (Mehlum, 1986;Bakken, 1991). Other potential origins such as the islands of Tristan da Cunha and Gough to the north-west (Williams, 1984;Fraser et al, 1988), Prince Edward and Marion to the northeast (Williams, 1984) and South Sandwich to the southwest (Croxall et al, 1984;Convey et al, 1999), are all at distances of 2000-2500 km away. South Georgia, the stronghold of the Antarctic Prion P. desolata with an estimated population of 22 million pairs (Croxall et al, 1984), is over 3000 km away.…”

Distribution and abundance of the Southern Fulmar Fulmarus glacialoides

“…Detailed systematic surveys have been undertaken recently (Poncet 1997;Convey et al 1999), confirming the importance of this island group for the global population. Many islands contained numerous breeding pairs, notably Visokoi Island, Montagu Island, Bristol Island (including Wilson, Grindle, and Freezland Rocks) and Cook Island.…”

“…In total, 80 confirmed and three possible breeding localities have been recorded and the global breeding population estimated at a minimum of 400,000 breeding pairs. Census data are lacking for seven of 80 breeding localities, but descriptive notes (Falla 1937;Robertson et al 1980;Convey et al 1999) suggest that their total breeding population probably comprises less than 1% of the estimated global breeding population. The current population estimate of 400,000 breeding pairs, based on the most recent and reliable counts (Table 1), should be interpreted as a minimum estimate.…”

“…Large colonies are typically counted by extrapolating estimates of snapshots of representative parts of the colony. Such estimates may deviate 40% or more from the estimated count (Poncet 1997;Convey et al 1999). The use of photography in future surveys could increase count precision if individual birds are counted from high quality images.…”