Data Zone
Justification of Red List category
The population has been stable or increasing recently throughout most of its breeding range, particularly in East Antarctica, the Ross Sea and on the southern Antarctic Peninsula south of 66° S (Sailley et al. 2013, Lyver et al. 2014, Southwell 2015a,b). This contrasts with the well-documented population decrease among colonies on the South Orkney Islands (Dunn et al. 2016) and on the west coast of the northern Antarctic Peninsula (e.g. Fraser et al. 1992, Lynch et al. 2012, Cimino et al. 2016a). Modelling exercises now replicate some of the strongest population changes observed (Che-Castaldo et al. 2017). East Antarctic regional and Ross Sea populations have almost doubled in abundance since the 1980s and have been increasing, or stable, since the earliest counts in the 1960s (Taylor and Wilson 1990, Wilson et al. 2001, Lyver et al. 2014, Southwell et al. 2015a, Southwell and Emmerson 2019). The population changes are associated with five-year lagged changes in the physical environment, suggesting that the changing environment impacts primarily on the pre-breeding age classes (Wilson et al. 2001, Southwell et al. 2015a,b). Recently, improved reporting of some large colonies, including mega-colonies on the Danger Islands (Borowicz et al. 2018), also highlight the probable stability of the colonies on the north eastern tip of the Antarctic Peninsula, though further studies would help reduce uncertainty in this region.
Currently, the net change in world population is positive (Lynch and LaRue 2014), which, along with the size of its total population numbering in the millions, qualifies the species to be listed as Least Concern. However, modelled projections suggest a future decrease at a circumpolar scale (Ainley et al. 2010). The species is considered to be an ice obligate (Ainley 2002), and recent population increases are coincident with increasing sea ice extent and coastal polynya persistence (cf Ainley et al. 2005, Massom and Stammerjohn 2010, Massonnet et al. 2015, Parkinson 2019), although at some sites, too much ice during critical times in the breeding season can reduce breeding success (Massom et al. 2006, Emmerson and Southwell 2008, Ropert-Coudert et al. 2018a). It will be important to review such coincident trends on a regular basis.
Population justification
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 breeding 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 breeding population to be 3.79 million pairs (range 3.52-4.10 million pairs) spread amongst 190-250 colonies (depending on the definition of a colony), equating to 7.58 million breeding individuals, based largely on satellite imagery of breeding colonies obtained between 2006 and 2011. These estimates do not include mature individuals that have skipped breeding in a season, which have been estimated to comprise up to 20% of the total breeding-age population (Southwell et al. 2017), nor pre-breeding individuals (the species not beginning to breed until an average of 4-5 years; Ainley 2002). The global population of breeding-aged individuals is thus likely to be around 10 million mature individuals; the total population including both mature and pre-breeding birds is around 14-16 million individuals (Southwell et al. 2017).
Trend justification
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. Satellite imagery broadened the scope of assessing colony population size. Recent direct surveys in East Antarctica (Southwell et al. 2015a, b) and the Ross Sea (Lyver et al. 2014) have estimated a greater increase in these regions (e.g. average rate of increase in East Antarctica 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%. The increase in numbers in the Ross Sea accelerated after about 2000 (Lyver et al. 2014).
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 (Lyver et al. 2014, Southwell et al. 2015a,b); the species has also been increasing on the southern Antarctic Peninsula south of 66°S (Sailley et al. 2013). In the northern Peninsula region, evidence indicates that some populations are beginning to stabilize after decades of significant decrease (Fountain et al. 2016); population decreases had previously occurred in parts of the northern Peninsula region (Fraser et al. 1992) and in the South Orkney Islands (Dunn et al. 2016). Modelling exercises now replicate some of the strongest signals in population change (Che-Castaldo et al. 2017). The net change in world population has been 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 decrease north of 70°S after the mid-21st century (Ainley et al. 2010, see also Cimino et al. 2016a), and such a change will necessitate a future re-examination of the Adélie Penguin’s status.
Pygoscelis adeliae breeds on land, but is a sea ice obligate species. It is found along the entire Antarctic coast and at some of its nearby islands. Individuals are dispersive in the post-breeding and winter periods, moving towards areas of persistent sea ice to moult after breeding (Trivelpiece and Fraser 1996, Ainley 2002, Clarke et al. 2003, Ainley et al. 2010, Hinke et al. 2014, Warwick-Evans et al. 2019). Many colonies are associated with polynyas as well as with cross-shelf troughs and canyons (Fraser and Trivelpiece 1996, Ainley 2002, Arrigo and van Dijken 2003).
Numbers are increasing in Victoria Land in the Ross Sea (Lyver et al. 2014) and in other areas of East Antarctica (Southwell et al. 2015a). 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 parts of the northern Peninsula region (Lynch et al. 2012, Fountain et al. 2016). Two mega-colonies on the Danger Islands (Borowicz et al. 2018) highlight the probable stability of the colonies in the colder north-eastern side of the Antarctic Peninsula, where sea ice prevalence has remained little changed. The net global population has increased over the last 30 years (Ainley et al. 2010, Lynch and LaRue 2014, Che-Castaldo et al. 2017). Analyses based on the modelling of climate effects indicates the possibility that the global population could start to decrease after the middle of the 21st century (Ainley et al. 2010, D. Ainley in litt. 2012). These projected decreases may only commence after a warming of 2.0°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 and the evolving skills of climate modelling (Ainley et al. 2010, Bronselaer et al. 2018).
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 at the time of arrival (Emmerson et al. 2011). Females lay one, or more usually two eggs, which are incubated by both sexes in alternating shifts.
The species mainly feeds on krill, fish, amphipods, cephalopods and jellyfish (Thiebot et al. 2016), though these latter three taxa are probably of minor importance. It captures such prey by pursuit-diving to maximally 150-180 m, with the majority of foraging down to 30 m (Watanuki et al. 1997, Lyver et al. 2011, Ropert-Coudert et al. 2018b), becoming deeper as shallow prey are depleted at least off large colonies (cf Ainley et al. 2015, Cimino et al. 2016b) during the summer breeding period. During winter, dives tend to be deeper than during summer (maximally to 130 m), with foraging constrained by short day-length (Takahashi et al. 2018). Adélie Penguins tend to winter far enough north that there is some daylight each day (Ballard et al. 2010), as they are hesitant to dive into the water during darkness for fear of not being able to see predators (Ainley and Ballard 2011).
The species is migratory. Patterns of movement are well-known for adults during breeding, with foraging within 10-180 km of the coast depending upon colony size (Ballance et al. 2009). Foraging trips can be as far as 380 km during the incubation period (Clarke et al. 2006). During the non-breeding period, adults move into the pack-ice up to 1,000-2,500 km from the breeding colony, depending upon the distance to the sea ice edge (e.g. Clarke et al. 2003, Ballard et al. 2010, Dunn et al. 2011, Hinke et al. 2015, Takahashi et al. 2018, Thiebot et al. 2019, Warwick-Evans et al. 2019). In most cases, this involves moving to the north, although individuals in the northern Antarctic Peninsula shift east or west, and those of the central western Antarctic Peninsula shift south; previously, when winter sea ice was more persistent, there was little movement, with many individuals remaining in the vicinity of their colony sites year round (Parmelee et al. 1977). Patterns of movement for juveniles are poorly known, but during their first year they remain in the pack-ice (Ainley et al. 1984).
The global population has been exhibiting a net increase (Lynch and LaRue 2014). The population on the west coast of the northern Antarctic Peninsula is beginning to stabilize after decades of significant decrease (Fountain et al. 2016). Recent reports of the sizes of the mega-colonies at the Danger Islands on the east ice-bound coast of the Antarctic Peninsula (Borowicz et al. 2018) also suggest that populations in this area are probably stable. Results of computer modelling work suggests that the net overall increase will continue in the near term, but that net population change may reverse in the future if climate change continues on its current track. An analysis by Ainley et al. (2010) indicates that owing to sea ice retraction, all colonies north of 67-68°S could be lost by the time that Earth's average tropospheric temperature reaches 2.0°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 2.0°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). More recent model predictions are consistent, though freshening of coastal water by ice-shelf melt may delay slightly the predicted overall decrease in Antarctic sea ice (Bronslaer et al. 2018). Colonies along the west coast of the Antarctic Peninsula that are experiencing novel conditions due to increased sea surface temperature and reduced sea ice seasonal persistence were found to be decreasing or to have an unknown trend, strongly supporting ongoing physical changes as a driver of population change in the species (Cimino et al. 2016a). 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, Emmerson and Southwell 2011, Hinke et al. 2014). However, a simple latitudinal gradient in sea ice loss is unlikely, as change so far has been regional in the Antarctic (Zwally et al. 2002, Turner et al. 2009, Massom and Stammerjohn 2010, Trathan et al. 2011, Fretwell et al. 2012). During the summer, nesting habitat in the Antarctic Peninsula has been affected by an increase in the incidence of severe snowfall (Fraser et al. 2013, Cimino et al. 2019), which is consistent with climate models (Turner et al. 2007, Ainley et al. 2010). On the basis of this and more recent modelling (Cimino et al. 2016a), as well as continuously improved understanding relating to climate change impacts (e.g. Fraser et al. 1992, 2013, Trathan et al. 2015, Ropert-Coudert et al. 2019), it will be vital to periodically review population responses to ongoing climate variability and change. It currently remains a challenge to extrapolate population trends, due to significant unexplained interannual variability in abundances (Che-Castaldo et al. 2017), suggesting improved understanding is needed about, for example, prey availability, competing species and demographic change (i.e. estimates of change in adult and juvenile survival, age of forest breeding or reproductive success by age).
Population trajectories in some locations have been considered in relation to the historical depletion and subsequent recovery of trophically competing cetacean or fur seal populations (Ainley et al. 2007, 2010, Trivelpiece et al. 2011) and possibly more recently the depletion of competing fish (Ainley et al. 2017). Further studies to understand foodweb connections that involve Adélie Penguins, their prey and species that compete for the same resource will be important, as such information will help in understanding unexplained interannual variability in abundance.
Flightlessness and proximity to Antarctic stations (over 1 million birds breed within 10 km of stations in East Antarctica; Southwell et al. 2017) and associated traffic makes the species susceptible to pollution (Culik et al. 1991) and mortality from oiling. For example, the 1989 Bahia Paraiso oil spill near Palmer (Culik et al. 1991) was estimated to have killed 16% of local penguins. The risk of future spills remains, with potential for similar local scale impacts (Trathan et al. 2015, J. Croxall in litt. 2017, Ropert-Coudert et al. 2019).
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 no ecosystem-based management is implemented to properly take into account the needs of species that feed upon krill (Agnew 1997). Relevant (overlapping) fisheries are CCAMLR-regulated, and though unlikely to overlap with the majority of the population (J. Croxall in litt. 2017, Trathan et al. 2018, Warwick-Evans et al. 2018), consideration will be needed where they do overlap. Protection of habitat on land and at sea remains important, with the designation of appropriate protection for transit, foraging and moulting. Increased understanding about the potential impact of tourism development on colonies in the northern part of the range will be important, given the growing number of tourists visiting the Antarctic (cf Dunn et al. 2019).
Conservation Actions Underway
This is one of the most studied penguin or seabird species (del Hoyo et al. 1992, Ainley 2002) and is the subject of on-going research throughout its circumpolar range. A number of breeding sites are designated as Antarctic Specially Protected Areas (ASPAs), especially in regions with human traffic. The foraging areas of some colonies are located within Marine Protected Areas (MPAs). The Ross Sea Region Marine Protected Area (RSR MPA) protects a number of colonies, though not moulting areas; other proposed MPAs elsewhere in Antarctica should afford protection for other colonies. Well-designated MPAs, coupled with protection at breeding sites, through either MPAs or ASPAs, are likely to be the most effective means for conservation, as both breeding sites and foraging areas will then be protected.
Human disturbance and scientific research are strictly regulated.
Conservation Actions Proposed
Continue to monitor population trends and relate to 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. Demographic research is needed, as is more work on the species's wintering ecology and its ecological, spatial and temporal overlap with fish and krill extraction. Improved understanding of all factors driving population change is needed, including for those species that potentially compete for the same prey resource as Adélie Penguins, whether recovering populations of seals, cetaceans or large fish. Such information will help to improve predictions of future environmental changes and how these will impact the species's population.
Text account compilers
Hermes, C., Martin, R., Trathan, P. N., Everest, J.
Contributors
Ainley, D., Ballard, G., Bost, C., Butchart, S., Calvert, R., Cimino, M., Croxall, J., Ekstrom, J., Emmerson, L., Garcia Borboroglu , P., Hinke, J., Kooyman, G., Lynch, H., Pearmain, L., Ropert-Coudert, Y., Southwell, C., Takahashi, A., Taylor, J. & Woehler, E.
Recommended citation
BirdLife International (2024) Species factsheet: Adelie Penguin Pygoscelis adeliae. Downloaded from
https://datazone.birdlife.org/species/factsheet/adelie-penguin-pygoscelis-adeliae on 28/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 28/11/2024.