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Site description (2015 baseline)

The Dion Islands are located in Marguerite Bay, ~14 km south of Adelaide Island, western Antarctic Peninsula, and lie around 12 km from IBA Avian Island. The group comprises several islands of less than 0.5 km across, with numerous islets, shoals and reefs. The IBA qualifies on the basis of the Imperial Shag (Phalacrocorax [atriceps] bransfieldensis) colony present and is defined by the boundary of ASPA No. 107: Emperor Island, Dion Islands.

The Dion Islands have several patches of permanent ice though are generally ice-free in summer. The geology consists of fine-grained lavas and tuffs, with shales, sandstones, grits and conglomerates also present (ASPA No. 107 Management Plan, 2002). Emperor Island, the second largest of the Dion Islands, is rocky and precipitous and less than 0.5 km across at its widest point. Vegetation comprises cryptograms and at least 19 species of lichen.

The nearest permanent scientific stations are Teniente Luis Carvajal Station (CHL, summer-only), situated ~14 km to the northwest on Adelaide Island and with capacity for ~30 personnel, and Rothera Station (GBR, year-round) also located on Adelaide Island 41 km to the northeast and with capacity for ~100 personnel.

No long-term meteorological records are available for the Dion Islands, although at Carvajal Station the mean daily maximum temperature was 3°C in February for the period 1962-74, with the mean daily minimum temperature being –8°C in August over the same period (ASPA No.107 Management Plan, 2002). This is similar to data recorded in 1949 by Stonehouse (1953, cited in ASPA No.107 Management Plan, 2002) at the Dion Islands. Winds prevail from a northerly direction, and most snowfall occurs between August and October, with light precipitation continuing through the summer. More recent analyses for nearby Rothera Station (GBR) have shown a distinct warming trend in the region, with an increase in annual average temperature of from -5°C in 1980 to -4°C in 2010 (Trathan et al. 2011).

Key biodiversity

All birds known to breed within the IBA have been recorded on Emperor Island. Approximately 500 pairs of Imperial Shag were recorded breeding on Emperor Island in the 1980s (S. Poncet pers. comm. 2005), and 810 pairs were recorded in a nest count in 2012 (Casanovas et al. in press). An Adélie Penguin (Pygoscelis adeliae) colony on Emperor Island was estimated at 700 pairs in 1987 (Poncet & Poncet 1987) and 1420 pairs in 2012 (Casanovas et al. in press).

A small Emperor Penguin (Aptenodytes forsteri) colony that formerly occupied a low-lying beach and rocky promontory in the southeast of Emperor Island is probably no longer present. First discovered on the island in 1948 (Stonehouse, 1953 cited in ASPA No.107 Management Plan, 2002), this was one of the most northerly Emperor Penguin colonies in Antarctica and one of only three sites where this species had been found breeding on land (Trathan et al. 2011). Stonehouse (1953) recorded around 150 breeding pairs on the island in the winter of 1949 and numbers are thought to have fluctuated around this level until 1968, after which they may have increased. However, only 14 males with eggs were present on the island in winter of 1999 (ASPA No. 107 Management Plan, 2002), whilst a count made from 1998 and 2005 aerial imagery indicated less than 20 Emperor Penguins remained breeding on the island (Fretwell & Trathan 2009). Further analysis of imagery acquired on 28 November 2009 showed no Emperor Penguins present (Trathan et al. 2011), and the birds probably no longer breed at the site.

Other confirmed breeders on Emperor Island include the Wilson's Storm-petrel (Oceanites oceanicus), Kelp Gull (Larus dominicanus) and Brown Skua (Catharacta antarctica) nesting on the larger islands (data cited in ASPA No.107 Management Plan, 2002). However, these species have not been censused owing to the difficult access.

Non-bird biodiversity: Leopard Seals (Hydrurga leptonyx) are occasionally observed in the Dion Islands, whilst Crabeater Seals (Lobodon carcinophagus) are commonly found on local ice floes. Weddell Seals (Leptonychotes weddellii) have also been recorded hauled out at Emperor Island (ASPA No. 107 Management Plan, 2002).

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Recommended citation
BirdLife International (2024) Important Bird Area factsheet: Emperor Island, Dion Islands (Antarctica). Downloaded from https://datazone.birdlife.org/site/factsheet/emperor-island-dion-islands-iba-antarctica on 29/11/2024.