The Rosenthal Islands group comprises approximately 80 small islands, the largest of which is Gerlache Island, which rises to ~100 m in height and is approximately 2.5 km by 1.2 km in size. The smaller islands are all <100 m in height, and generally <500 m across. Gerlache Island is mostly covered by a permanent ice cap, while the smaller islands are generally ice-free. A number of promontories extend from the adjacent Anvers Island coastline, and many of these are also partly ice-free. The ice-free ground provides habitat suitable for breeding birds and vegetation (predominantly mosses and lichens). The ASPA and IBA boundaries extend ~8 km south of the main Rosenthal Islands group to include ~35 ice-free islands and peninsulas that also host breeding birds.
The islands and peninsulas within the region are generally rocky, rugged and exposed, with the more seaward islands tending to be steeper and with shorelines that are inaccessible to all but flying birds. The coastlines are irregular, with numerous offshore islets and rocks, most of which are uncharted. A number of islands and peninsulas close to Anvers Island are of more gentle topography and have more accessible coastlines, making them suitable for penguins to establish colonies.
No meteorological data are available for the Rosenthal Islands, although at nearby Palmer Station the mean annual temperature was –1.8° C between 2010-17, with an average monthly air temperature in August of –5.94° C, and in January 1.72° C.
The nearest permanent scientific station is Palmer (USA), situated ~20 km to the east at Arthur Harbour, southern Anvers Island. See IBA Cormorant Island for more information on Palmer Station and local climate.
The Gentoo penguin population was recorded as 7324 breeding pairs in 2012/13, which qualifies under IBA Criterion A4, ≥1% of the global population of this species. More recent counts have covered only selected islands, although show large numbers of Gentoo penguins continue to breed in the area. The 2012/13 count remains the most recent for the whole group of islands.
In addition to the Gentoo penguin, at least seven other species of bird breed in the Rosenthal Islands: Adélie penguin (Pygoscelis adeliae), Chinstrap penguin (Pygoscelis antarctica), Southern Giant petrel (Macronectes giganteus), Antarctic tern (Sterna vittata), Imperial shag (Leucocarbo atriceps bransfieldensis), Kelp gull (Larus dominicanus) and South Polar skua (Stercorarius maccormicki). Wilson’s Storm petrels (Oceanites oceanicus) are common and probable breeders. Snowy sheathbills (Chionis alba) are present in small numbers at penguin and shag colonies, and although nesting has not been observed may also breed in the Area. Snow petrels (Pagodroma nivea) are common although are not known to breed in the area.
Non-bird biodiversity: Mammals such as Elephant (Mirounga leonina), Weddell (Leptonychotes weddellii) and Antarctic fur (Arctocephalus gazella) seals may haul out on accessible beaches. The vegetation of the Rosenthal Islands has yet to be described in detail, although several species of mosses and lichens have been identified on the islands where habitat suitable for vegetation is relatively scarce because of the intensive occupation by breeding penguins. Vegetation appears to be more widespread on islands yet to be surveyed. The two Antarctic flowering plants, the grass Deschampsia antarctica and the pearlwort Colobanthus quitensis, are probably present based on their colonisation of nearby islands. Several species of invertebrates colonise ice-free areas within the island group (Gantz et al., 2018).
Pressure/threats to key biodiversity
The IBA shares the boundary of an Antarctic Specially Protected Area (ASPA) proposed for designation under the Antarctic Treaty System (designation had to be deferred when the 2020 Antarctic Treaty meeting was cancelled and will be considered in 2021). The ASPA provides a Management Plan to coordinate activities in the region. The Management Plan prohibits entry to the ASPA except by a permit issued by a national authority for compelling scientific and management reasons. Tourism, recreation and overflights of <2000 ft (~610 m) are prohibited from the area. More information on the regional environment and scientific programmes, and the broad conservation issues can be found in the Management Plan for the ASPA, and also for ASMA (Antarctic Specially Managed Area) No. 7.
Conservation responses/actions for key biodiversity
Conservation measures are included in the ASPA Management Plan.
Proposed as Antarctic Specially Protected Area No.? Rosenthal Islands. The IBA and ASPA lie within Antarctic Specially Managed Area (ASMA) No.7 Southwest Anvers Island and Palmer Basin.
Habitat and land use
Uninhabited wilderness, extremely remote and difficult to access. Proposed to be designated as Antarctic Specially Protected Area No.? Rosenthal Islands.
International area managed under the framework of the Antarctic Treaty System.
BirdLife International (2020) Important Bird Areas factsheet: Rosenthal Islands. Downloaded from
http://www.birdlife.org on 23/11/2020.