Ryder Bay is 6 nautical miles (11 km) wide at its mouth and indenting 4 nautical miles (7 km) on the southeast coast of Adelaide Island. Rothera Point and most islands in the IBA have patches of persistent snow, and Léonie Island (max. height 502 m a.s.l.) has a large permanent ice cap. Rothera Point and the islands are rocky, with irregular coastlines including beaches, steep cliffs, scattered rocks and boulders, providing extensive ice-free ground and crevices for nesting petrels. Several ephemeral freshwater ponds, meltwater channels and small streams are present, particularly on Léonie Island. Vegetation is sparse and dominated by lichens and mosses.
A permanent scientific station and gravel runway is located at Rothera Point on Adelaide Island and operates year-round. The station has capacity for 130 people and is occupied by c.20 people over winter. Several of the Ryder Bay islands are visited by station personnel for the purposes of science and recreation. There are also occasional tourist landings on Anchorage, West and East Lagoon Islands. The climate is cold and dry, and represents a transition from that typical of the more maritime conditions to the north (influenced by the ocean) and the extremes of continental Antarctica to the south. A programme of surface synoptic meteorological measurements commenced at Rothera Research Station in 1977; mean monthly air temperatures range between c. -10.5 and + 1.4 °C, with the prevailing wind from the north-north-east and averaging 12.1 m s-1.
Rothera Point and the islands in Ryder Bay held 978 occupied territories of south polar skuas (Catharacta maccormicki), 259 south polar skuas at club sites and 405 pairs of Antarctic shags (Leucocarbo [atriceps] bransfieldensis) in 2018 (Phillips et al. 2019). Numbers of skua territories were as follows: Rothera Point (25), Killingbeck Island (17 and one territory on adjacent islet), Léonie Island (266, and 58 skuas at a club site), Kirsty Island (24), West Lagoon Island (29), East Lagoon Island (151, and 65 skuas at a club site), Anchorage Island (439, one territory on adjacent islet and 136 skuas at two club sites), Donnelly Island (25). Antarctic shags bred on three islands: Killingbeck Island (74 pairs), Mucklescarf Island (251 pairs) and Skart Island (80 pairs). Skua territories were widely distributed across snow-free ground except on the scree above 100 m on Léonie Island. Other breeding species are Kelp Gulls (Larus dominicanus) including at Rothera Point (4 pairs), East and West Lagoon Islands (15-25 pairs), Anchorage Island (10-20 pairs), Léonie Island (20-30 pairs), Donnelly Island (10-20 pairs), Killingbeck Island (5-10 pairs) and Kirsty Island (20-30 pairs); all counts in 2018 (British Antarctic Survey unpublished data).
Around 10 pairs of Antarctic Tern (Sterna vittata) bred on Léonie Island, but not elsewhere in the IBA in 2018 (British Antarctic Survey unpublished data). Antarctic terns did, however, breed at Rothera Point prior to runway construction, and in small numbers on Killingbeck, Lagoon and Anchorage Islands in the 1990s (Milius 2000). Wilson's Storm-petrels (Oceanites oceanicus) bred at Rothera Point, Anchorage and Léonie Island in 2018 - confirmed by records of adults calling from crevices in daylight or a bird seen incubating - and are highly likely to breed on East Lagoon Island given the large extent of suitable habitat. Moulting Adélie penguins (Pygoscelis adeliae) are present (10s of birds) at Rothera Point, Anchorage, West Lagoon and East Lagoon islands in the late summer.
Non-bird biodiversity: large numbers (>100) of moulting elephant seals (Mirounga leonina), up to 100 Antarctic fur seals (Arctocephalus gazella) and 10s of Weddell seals (Leptonychotes weddellii) and crabeater seals (Lobodon carcinophaga) occur on land or adjacent floating ice at Rothera Point and the islands in the summer.
Pressure/threats to key biodiversity
The scientific station buildings are immediately adjacent to the skua breeding sites at Rothera Point. There are multiple antennae and steel guy-wires in the nesting area, which kill or seriously injure one or more skuas in most years. Around 30% of the area occupied by skuas at Rothera Point was designated as an Antarctic Specially Protected Area No. 129 in 1985. The site is protected as a control area against which to compare human impacts (ASPA No. 129 Management Plan, 2017). A proposal was submitted to the Antarctic Treaty Consultative Meeting in 2018 to designate western Léonie Island, East Lagoon, Mucklescarf, Anchorage and Donnelly islands as a new ASPA. This would encompass c.80% of the skuas and 62% of the shags breeding in the IBA.
Human disturbance to the skuas at Rothera Point is generally low during the breeding season because of restricted access; however, prolonged presence of humans associated with construction work close to skua nests has caused occasional nest desertion and breeding failure. Occasional mortality of skuas has also resulted from collision with planes on the runway, which is used as a loafing site by nonbreeding birds. Irrespective of these low-level impacts, at Rothera Point the number of breeding pairs of skuas increased from 11 to 24 between 1975/76 and 2017/18 (overall 1.9% per annum) and of occupied territories (i.e. including nonbreeding birds holding territory) from 17 to 25 between 1988/89 and 2017/18 (overall 1.3% per annum) (Phillips et al. 2019). The isolation of the islands reduces visitor numbers and associated disturbance of wildlife.
Richard Phillips, British Antarctic Survey.
BirdLife International (2023) Important Bird Areas factsheet: Ryder Bay Islands. Downloaded from
http://www.birdlife.org on 28/03/2023.