Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (extent of occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
Convey et al. (1999) estimate a world population of ~4 million breeding pairs.
The species expanded its range and its population in the mid-20th century, potentially owing to increased prey (krill) availability (del Hoyo et al. 1992). It is currently decreasing at most sites on the Antarctic Peninsula, except at the southern extreme of its range where it is increasing. It is stable at South Sandwich Island (Lynch et al. 2016). The population trend is unknown at many other locations.
This species has a circumpolar distribution, being found in Antarctica, the South Sandwich Islands (Islas Sandwich del Sur), the South Orkneys, South Shetland and South Georgia (Georgia del Sur), Bouvet Island (to Norway) and the Balleny Islands (del Hoyo et al. 1992).
Population information for many sites is unknown or out of date. For example, population surveys at the South Sandwich Islands, where the majority of the world population breeds (1,500,000 pairs; Convey et al. 1999; Lynch et al. 2016), are infrequent. Other important breeding populations exist at the South Orkney Islands (927,000 pairs; Poncet and Poncet 1985, Humphries et al. 2017), but this is probably an underestimate (P. Trathan in litt. 2017), especially at the western end of the archipelago. Large populations also occur at the South Shetland Islands (987,000; Trivelpiece and Trivelpiece 2013) and the west Antarctic Peninsula (72,000; Trivelpiece and Trivelpiece 2013). Small populations occur at South Georgia (~1,800 pairs), Bøuvet (<100) and at the Balleny Islands (< 100) (Trivelpiece and Trivelpiece 2013). At the Antarctic Peninsula, population estimates are now increasingly out of date (Trathan et al. 2019).
This species is mostly found in zones with light ice pack. Its diet is comprised almost exclusively of Antarctic krill, but it will also take fish and other species of crustaceans when possible. Prey capture is apparently by pursuit-diving up to a depth of 70 m, but mostly at depths less than 45 m. It breeds on irregular rocky coasts in ice free areas, forming large colonies of hundreds and thousands of birds (del Hoyo et al. 1992). Winter migrations can be extensive and winter habitats are generally pelagic and are located north of the sea ice edge (Hinke et al. 2015, 2019).
Climate change is potentially the greatest threat to this species at present and in the future. It is thought to impact reproductive success through incurring changes in abundance and distribution of krill (Trivelpiece et al. 2011, Clucas et al. 2014), though these effects have been noted only in parts of the range (Lynch et al. 2016). Changes in krill biomass and availability resulting from habitat shifts are thought to be driving rapid declines at a number of colonies (Barbosa et al. 2012, Lynch et al. 2012, Naveen et al. 2012, Dunn et al. 2016). In addition, there is considerable overlap between the expanding krill fishery and the species’s foraging distribution, hence there is potential for resource competition, potentially aggravating the climatic effects on krill availability (Hinke 2017, Warwick-Evans et al. 2018; Trathan et al. 2018).
Volcanic activity during the 2016 moulting season at Zavodovski and Bristol in the South Sandwich Islands could have had severe impacts on the large colonies residing there, and surveys of the breeding colonies at the South Sandwich Islands should be repeated. If large numbers are found to have been killed by the volcanic event, and if declines elsewhere on the Antarctic Peninsula continue, the species may warrant uplisting.
Human impacts potentially include disturbance from tourists, scientists, construction of new science facilities and fisheries. However, only a very small percentage of the global population is exposed to human intrusion and there is currently no documented evidence of population-level impacts (J. Croxall in litt. 2017).
Conservation Actions Underway
Long-term monitoring programmes are in place at several breeding colonies. In the Antarctic, visitor site guidelines specify minimum approach distances of 5 meters and off-limit areas.
Conservation Actions Proposed
Continue/extend long-term monitoring of breeding colonies (Trathan et al. 2019). Monitoring studies of chinstrap populations must include annual censuses, dietary and foraging studies, reproductive research, and demographic data. Currently this information is available only from the South Shetland Islands and intermittently from the South Orkney Islands and the Palmer Archipelago. Establish similar research efforts in the South Sandwich Islands and increase research efforts in the South Orkney Islands. Gather data from the edge of the species range at South Georgia and along the Antarctic Peninsula near the southern extent of this species’ distribution. Collect information from all of these main breeding regions on distribution and diet during the non-breeding winter period. Minimize disturbance to breeding colonies. Protection of habitat on land and at sea remains important, with the designation of appropriate protection for transit, foraging and rafting areas at sea.
Text account compilers
Martin, R., Trathan, P. N., Calvert, R., Moreno, R., Pearmain, L.
Ballard, G., Butchart, S., DuBois, L., Ekstrom, J., Fraser, W., Garcia Borboroglu , P., Hinke, J., Lynch, H., Makhado, A., Schmidt, A., Schneider, T. & Trathan, P. N.
BirdLife International (2022) Species factsheet: Pygoscelis antarcticus. Downloaded from http://www.birdlife.org on 22/05/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/05/2022.