Signy Island

Year of compilation: 2015

Site description

Signy Island lies 1.6 km southwest of Cape Hansen on the south coast of Coronation Island. The IBA qualifies on the basis of the Chinstrap Penguin ( Pygoscelis antarctica ), Adélie Penguin ( P. adeliae ), Imperial Shag ( Phalacrocorax [ atriceps ] bransfieldensis ), Antarctic Prion ( Pachyptila desolata ), Brown Skua ( Catharacta antarctica ), Wilson's Storm-petrel ( Oceanites oceanicus ), and Southern Giant Petrel ( Macronectes giganteus ) colonies present. The IBA comprises all of Signy Island and several offshore islands including Confusion Island, Oliphant Islands, Spindrift Rocks and Shagnasty Island.

Almost half of Signy Island is covered by a permanent ice cap, with the highest point on the island being Tioga Hill (278 m). The coastline is dominated by exposed crags, and rocky headlands, with intervening bouldery slopes and sizeable moss banks (Tickell 1962). There are 16 lakes on the island and several glaciers, the largest of which terminates on the southern coast.

Extensive moss turfs occur particularly on the northwest coast of Signy Island, forming primary breeding habitat for burrowing petrels (R. Fijn pers. comm. 2011). Other flora on Signy Island includes Antarctic Hairgrass ( Deschampsia antarctica ) and Antarctic Pearlwort ( Colobanthus quitensis ), ~50 moss species, ~12 liverworts and ~120 lichen species (BAS, Signy Island Research Station, accessed 02/09/2010). Algae and cyanobacteria have also been observed in wetter sites on the island (Broady 1979).

The winter climate on Signy Island is influenced by pack ice which extends to surround the island from the Weddell Sea. Over summer pack ice retreats and Signy Island has a maritime climate. Mean summer air temperatures are between –2°C to 3°C, whilst during winter the mean monthly air temperature ranges from –2°C to –17° C. Strong winds are frequent, prevailing from the west. The minimum winter temperature on record is –39.3°C, whilst in summer temperatures range from –7°C to 19.8°C.

Signy Research Station (GBR) is located midway along the eastern shoreline of Signy Island, on the southern side of Borge Bay. The summer-only station accommodates ~8 people (COMNAP, Antarctic Facilities, accessed 31/08/2010).

Key biodiversity

An exceptionally diverse range of seabirds and waterbirds breed on Signy Island, including three species of penguin, four petrel species, two storm-petrel species, shags, sheathbills, two species of skua, gulls and terns.

Approximately 19 530 breeding pairs of Chinstrap Penguin breed on Signy Island (BAS unpublished data, M. Dunn pers. comm. 2010), with the most concentrated breeding sites on Gourlay Peninsula, an ice-free gently sloping peninsula on the southeast side of Signy Island; Pandemonium Point, on the southwest coast of Signy Island; Confusion Island, 100 m off the south of the island; and North Point (Croxall & Kirkwood 1979). This recent count is likely to be an under-estimate of typical Chinstrap breeding numbers, since this season was reportedly a poor one for this species (M. Dunn, pers. comm. 2011). Approximately 16 900 pairs of Adélie Penguin also breed at Gourlay Peninsula and North Point (Dunn et al . 2010), and 753 pairs of Gentoo Penguin ( Pygoscelis papua ) were recorded breeding for all Signy Island in 2010 (BAS unpublished data, M. Dunn pers. comm. 2010). Macaroni Penguins ( Eudyptes chrysolophus ) have not been recorded breeding on Signy Island or its offshore islands for many years, and were last observed breeding in low numbers (11 pairs) in 1979 (Croxall, Rootes & Price 1981).

Imperial Shags breed on ledges of low cliffs on the north coast of Signy Island and constituted 280 pairs in 2006/07 (R. Fijn pers. comm. 2011). Three larger groups of Imperial Shag may breed on flat or shallow-sloping areas on two islets near Shagnasty Island, as Rootes (1988) reported a total of 729 pairs in this area in the mid-1980s, although more recent data on these colonies are not available.

The latest survey in 2005/06 revealed 2351 pairs of Southern Giant Petrel breeding on Signy Island, predominantly on the western coast (M. Dunn & R. Fijn unpublished data, 2006). Approximately 1093 breeding pairs were recorded at North Point, G.P. Ridge and Borge Bay in 1984 (Patterson et al . 2008).

High numbers of Wilson's Storm-petrel breed on Signy Island in crevices and between boulders in ice-free areas, and it has been estimated that up to 200 000 breeding pairs were present on the island in 1966-68 (Beck & Brown 1972). It was also estimated that approximately 50 000 pairs of Antarctic Prion ( Pachyptila desolata ) breed on Signy Island, concentrated at Borge Bay on the eastern coastline close to Signy Station (Tickell 1962) and on the western coast from Foca Cove towards North Point (R. Fijn pers. comm. 2015). However, accurate counts of these species are difficult and numbers are approximate.

Approximately 100 pairs of Brown Skua ( Catharacta antarctica ) and a small number of South Polar Skua ( Catharacta maccormicki ) breed on Signy Island (Ritz et al . 2006). In addition, 195 pairs of Snow Petrel ( Pagodroma nivea ) were recorded breeding on Signy Island in 1985 (Croxall et al . 1995), although more recently numbers were estimated to exceed 1000 pairs (R. Fijn unpublished data, 2006).

Other birds breeding on Signy Island include the Cape Petrel ( Daption capense ), Snowy Sheathbill ( Chionis albus ), Kelp Gull ( Larus dominicanus ), Antarctic Tern ( Sterna vittata ) and Black-bellied Storm-petrel ( Fregetta tropica ) (BAS: Signy Island Research Station, 2010).

Non-bird biodiversity: Antarctic Fur Seals (Arctocephalus gazella) haul out in large groups around the coast of Signy Island, concentrated on the eastern and southern coastline, with an estimated 12 245 individuals present in February 2009 (BAS unpublished data, M. Dunn pers. comm. 2009), although numbers vary and reached over 21 000 in 1994 (Waluda et al. 2009). Weddell Seals (Leptonychotes weddellii) breed on sea-ice around Signy Island over the winter, and Southern Elephant Seals (Mirounga leonina) regularly pup in spring (BAS 2010). Southern Elephant Seals and Weddell Seals are common on Signy Island: 522 and 12 respectively counted in Feb 2006 (M. Dunn & R. Fijn unpublished data, R. Fijn pers. comm. 2015), and 309 and 5 respectively in 2009 (BAS unpublished data, M. Dunn pers. comm. 2010). Leopard (Hydrurga leptonyx) and Crabeater (Lobodon carcinophagus) seals are regularly seen on ice-flows around the island.

Pressure/threats to key biodiversity

A long-term penguin monitoring program is conducted at Signy Island as part of the CCAMLR Ecosystem Monitoring Program (CEMP). The three species of penguins are surveyed annually to determine population size, breeding success, and diet. Populations of Chinstrap and Adélie Penguins have declined substantially over the past three decades. The decrease in Adélie Penguin numbers between 1987 and 2010 is possibly linked to regional warming and changes in sea ice extent experienced over the same time period (Forcada et al. 2006).

Recommended citation
BirdLife International (2020) Important Bird Areas factsheet: Signy Island. Downloaded from on 23/11/2020.