Justification of Red List Category
The population has been increasing recently, particularly in East Antarctica (where most of the world population breeds) and the Ross Sea (Lyver et al. 2014, Southwell et al. 2015a, b) and on the southern Antarctic Peninsula south of 66° S (Sailley et al. 2013). However, modelled projections suggest a future decline. Currently, the net change in world population is positive (Lynch and LaRue 2014), which qualifies the species to be listed as Least Concern.
The total global population was previously estimated at c.2.37 million breeding pairs (range 1.83-2.88 million pairs) equating to 4.74 million mature individuals, based on survey data collated up to the mid-1990s (Woehler 1993, Woehler and Croxall 1997). More recently, Lynch and La Rue (2014) estimated the global population to be 3.79 million pairs (range 3.52-4.10 million pairs), equating to 7.58 million mature individuals, based on satellite imagery obtained between 2006 and 2011.
Lynch and LaRue (2014) reported that the global population had increased between the times of the two global estimates in the mid-1990s and 2014 (Woehler 1993, Woehler and Croxall 1997, Lynch and La Rue 2014), with 27% of the difference accounted for by increasing abundance at known colonies and 32% of the difference accounted for by colonies that had not previously been surveyed. Recent direct surveys in East Antarctica (Southwell et al. 2015a, b) have estimated a greater increase in this region (average rate of increase of 1.9% (1.3%-2.4%) per year over 30 years), indicating that the increase in the global population is probably greater than the 27%.
Recent population increases were found in those regions where most of the world population breeds, including East Antarctica and Victoria Land in the Ross Sea (Southwell et al. 2015a, b, Lyver et al. 2014); the species is now also increasing on the southern Antarctic Peninsula south of 66° S (Sailley et al. 2013). In the northern Peninsula region, there is also new evidence that some populations are beginning to stabilize after decades of significant decrease (Fountain et al. 2016); population decreases had previously occurred in the northern Peninsula region (Fraser et al. 1992). The net change in world population is now positive (Lynch and LaRue 2014). It should be noted that modelled projections in response to climate change, with associated inherent uncertainty, suggest that populations could decline north of 70ᵒS in the future (Ainley et al. 2010, see also Cimino et al. 2016), and such decline will necessitate a future re-examination of the Adélie Penguin’s status.
Pygoscelis adeliae is found along the entire Antarctic coast and at some of its nearby islands. Individuals are dispersive, moving towards areas of persistent sea ice to moult after breeding (Ainley et al. 2010). Numbers are increasing in Victoria Land in the Ross Sea and in other areas of East Antarctica. They are also increasing in the southern Antarctic Peninsula regions (Sailley et al. 2013, Lyver et al. 2014, Southwell et al. 2015a), but are decreasing or stable in the northern Peninsula region (Lynch et al. 2012, Fountain et al. 2016). The net global population has increased over the last 30 years (Ainley et al. 2010, Lynch and LaRue 2014). Analyses based on the modelling of climate effects suggests that the global population could start to decline in a few decades time (Ainley et al. 2010, D. Ainley in litt. 2012). These projected declines may only commence after a warming of 2°C above pre-industrial levels has been reached; the projected overall global trend will potentially be positive before this point (D. Ainley in litt. 2012). There still remains considerable uncertainty in these projections, due to the inherent difficulty of modelling the species complex interactions with both physical and biological processes.
This species nests on ice-free rocky coasts, often in extensive open areas to accommodate typically large colonies, which may be far from the open sea. Females lay two eggs, which are incubated by both sexes in alternating shifts. The species mainly feeds on krill, fish, amphipods and cephalopods. It captures such prey by pursuit diving, to about 150 m, though with the majority of foraging down to 50 m (Lyver et al. 2011).
The current global population is exhibiting a net increase, while that portion in the northern Antarctic Peninsula is beginning to stabilize after decades of significant decrease (Fountain et al. 2016). Computer modelling work suggests that these trends will continue in the near term but net population change may reverse in the future if climate change continues on its current track. An analysis carried out by Ainley et al. (2010) suggests that all colonies north of 67-68°S could be lost by the time that Earth's average tropospheric temperature reaches 2°C above pre-industrial levels, with negative impacts on all colonies north of 70°S, despite limited growth south of 73°S. In this study, 2042 is the median year (range 2025-2052) at which a 2°C warming is predicted, based on the four climate models in the IPCC Fourth Assessment Report (AR4) that most closely replicate recent environmental conditions and trends in the Southern Ocean (Ainley et al. 2010). Colonies experiencing novel conditions due to increased sea surface temperature were found to be declining or to have an unknown trend, strongly supporting ongoing environmental changes as a driver of population decline in the species (Cimino et al. 2016). Furthermore, annual migration and winter survival may be negatively affected by decreases in sea ice coverage at northern latitudes (Ainley et al. 2010, Ballard et al. 2010, Hinke et al. 2014). However, a simple latitudinal gradient in sea ice loss is unlikely, as warming so far has been regional in the Antarctic (Zwally et al. 2002, Turner et al. 2009, Trathan et al. 2011, Fretwell et al. 2012). During the summer, nesting habitat could be affected by an increase in the incidence of severe snowfall (Fraser et al. 2013). On the basis of this and more recent (Cimino et al. 2016) modelling work, as well as continued revelations concerning climate change (e.g. Fraser et al. 1992, 2013, Trathan et al. 2015), it will be vital to periodically review population responses to ongoing climate variability and change.
Flightlessness and proximity to Antarctic stations and associate traffic makes the species susceptible to pollution (Culik et al. 1991) and has previously suffered mortality from oiling, with the 1989 Bahia Paraiso oil spill near Palmer (Culik et al. 1991) estimated to have killed 16% of local penguins. The risk of future spills remains, with potential for similar local scale impacts (J. Croxall in litt. 2017).
The location of research stations near colonies has also led to reductions in suitable ground for breeding, excessive visits to colonies and disturbance caused by aircraft movements (del Hoyo et al. 1992), although the impact of disturbance in relation to environmental conditions appears to vary with location (Bricher et al. 2008) and only impacts a small minority of sites. Human impacts potentially include disturbance from tourists, scientists, construction of new science facilities and fisheries, particularly those targeting Antarctic krill. Harvesting of krill could be a threat, if management does not adequately take into account the needs of species that feed upon krill (Agnew 1997). However, relevant (overlapping) fisheries are CCAMLR-regulated and unlikely to overlap with a majority of the population (J. Croxall in litt. 2017). Protection of habitat on land and at sea remains important, with the designation of appropriate protection for transit, foraging and rafting areas at sea.
Conservation Actions Underway
This is one of the most thoroughly studied penguin species (del Hoyo et al. 1992) and is the subject of on-going research throughout its circumpolar range. Some colonies are located within protected areas. Human disturbance and scientific research are strictly regulated.
Conservation Actions Proposed
Continue to monitor population trends. Continue to closely monitor trends in the extent and persistence of sea ice, and associated climatic variables. Carry out further research into the species's ecology to improve understanding of how environmental changes and human activities, such as fishing, will affect the population. Improve predictions of future environmental changes and how these will impact the species's population, and conduct research into the potential effects of fish and krill extraction (D. Ainley in litt. 2012). Continue international work to tackle the drivers of projected climate change.
Text account compilers
Ekstrom, J., Martin, R., Butchart, S., Pearmain, L., Calvert, R., Taylor, J.
Woehler, E., Croxall, J., Kooyman, G., Garcia Borboroglu , P., Ainley, D.
BirdLife International (2020) Species factsheet: Pygoscelis adeliae. Downloaded from http://www.birdlife.org on 22/10/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/10/2020.