Cape Denison is a rocky point at the western entrance to Commonwealth Bay, George V Land. The Cape extends ~1.5 km in width and ~1 km inland, rising to meet the permanent continental icecap at a height of around 40 m. Several valleys, oriented northwest/southeast, contain a number of small glacial lakes, and melt streams can form in summer. Cape Denison served as a base for the Australasian Antarctic Expedition of 1911-14, and a number of historic relics from this era remain. Cape Denison was designated as ASMA No.3 in 2004, although in 2014 this was replaced by an enlargement of ASPA No.162 Mawson's Huts, Cape Denison, to include all of the original ASMA within the boundary of the protected area. The main reason for protection is the site's historic values, although environmental features such as the lakes, flora, mammals and the breeding birds are also listed as of importance (ASPA No.162 Management Plan 2014).
The IBA qualifies on the basis of the concentration of seabirds present (in particular Adélie Penguin (Pygoscelis adeliae)) and coincides with the boundary of ASPA No.162.
There are no research stations nearby. The closest permanent station is Dumont d'Urville, ~120 km to the west in Terre Adélie.
The management plan for ASPA No. 162 (2014) gives 18 800 breeding pairs of Adélie Penguin present at Cape Denison, although the year and source of data are not given. The satellite image analysis by Lynch & LaRue (2014) gave an estimate of ~13 834 breeding pairs (95% CI 8377, 22 671) (February 2011). The penguins nest mainly on the eastern and western coasts of Cape Denison, although are also found in smaller numbers along the northern coast.
Map C of the 2014 management plan shows Snow Petrel ( Pagodroma nivea ) and Wilson's Storm-petrel ( Oceanites oceanicus ) breeding on elevated ridges across the cape. A solitary pair of Cape Petrels ( Daption capense ) was reported breeding in 1982 (Woehler & Johnstone 1991), which appears to be shown at the eastern extremity of the cape on a map of Cape Denison (Australian Antarctic Data Centre 2010). At least several pairs of Antarctic Prions ( Pachyptila desolata ) were observed nesting at Cape Denison in 1913 by the Australasian Antarctic Expedition. A pair and a single bird were shot for museum collections, although Antarctic Prions have not been observed at Cape Denison since; this is the only record of Antarctic Prions breeding on the continent apart from the Antarctic Peninsula (Ensor & Bassett 1987). The number of birds breeding at Cape Denison are summarised in Table 157.1. Other non-breeding bird species recorded at Cape Denison include Southern Giant Petrel ( Macronectes giganteus ) and Emperor Penguin ( Aptenodytes forsteri ) (ASPA No. 162 Management Plan 2014).
Non-bird biodiversity: Weddell (Leptonychotes weddellii), Southern Elephant (Mirounga leonina) and Leopard (Hydrurga leptonyx) seals are reported to haul out at Cape Denison. Southern Elephant Seals also remain in the area to moult (ASPA No. 162 Management Plan 2014).
BirdLife International (2019) Important Bird Areas factsheet: Cape Denison. Downloaded from http://www.birdlife.org on 21/03/2019.