Introduction
King penguins (Aptenodytes patagonicus Miller) breed on sub-Antarctic islands near the Antarctic polar front (Bost et al., Reference Bost, Delord, Barbraud, Cherel, Pütz, Cotté, Weimerskirch, Borboroglu and Boersma2013; Marchant & Higgins, Reference Marchant and Higgins1990; Martínez, Jutglar, & Garcia, Reference Martínez, Jutglar, Garcia, del Hoyo, Elliott, Sargatal, Christie and de Juana2018; Williams, Reference Williams1995). Populations are distributed as far north as the Prince Edward Islands (46°S) in the Southern Ocean, the Falkland Islands (51°S) in the Atlantic Ocean, and Macquarie Island (54°S) in the southwestern Pacific Ocean (e.g. Bost et al., Reference Bost, Delord, Barbraud, Cherel, Pütz, Cotté, Weimerskirch, Borboroglu and Boersma2013; Pistorius, Baylis, Crofts, & Pütz, Reference Pistorius, Baylis, Crofts and Pütz2012; Pistorius et al., Reference Pistorius, Hindell, Crawford, Makhado, Dyer and Reisinger2017). In autumn and winter, when food is less abundant near colonies, the penguins often undertake long journeys towards the marginal ice zone (Bost, Charrassin, Clerquin, Ropert-Coudert, & Le Maho, Reference Bost, Charrassin, Clerquin, Ropert-Coudert and Le Maho2004; Pütz et al., Reference Pütz, Trathan, Pedrana, Collins, Poncet and Lüthi2014). Numerous birds have also been recorded in the area of the South Shetland Islands (62°S, 58°W) in the summer season. The first mention of king penguins in the archipelago dates back to reports by nineteenth century explorers (Eights, Reference Eights1833; Fildes, Reference Fildes1821). However, although Eights (Reference Eights1833) reported “many” king penguins, a century later Roberts (Reference Roberts1939) stated that king penguins were no longer found on the South Shetland Islands. Since then, there have been sightings (e.g. Furse & Bruce, Reference Furse and Bruce1975; Lange & Naumann, Reference Lange and Naumann1989; Lumpe & Weidinger, Reference Lumpe and Weidinger2000; Peter, Kaiser, & Gebauer, Reference Peter, Kaiser and Gebauer1988; Peter et al., Reference Peter, Braun, Janowski, Nordt, Nordt and Stelter2013) and records of breeding attempts at the archipelago (Juáres et al., Reference Juáres, Negrete, Mennucci, Perchivale, Santos, Moreira and Coria2014; Juáres, Ferrer, Coria, & Santos, Reference Juáres, Ferrer, Coria and Santos2017; Petry, Basler, Valls, & Kruger, Reference Petry, Basler, Valls and Kruger2013). The increased number of breeding attempts and observations in the Antarctic Peninsula region are probably related to climate change in the region, and potentially to the increase of the global population of this species (Juáres et al., Reference Juáres, Negrete, Mennucci, Perchivale, Santos, Moreira and Coria2014, Reference Juáres, Ferrer, Coria and Santos2017; Petry et al., Reference Petry, Basler, Valls and Kruger2013), although the population in the southern Indian Ocean sector has fluctuated (Weimerskirch, Le Bouard, Ryan, & Bost, Reference Weimerskirch, Le Bouard, Ryan and Bost2018).
The global population of king penguins decreased significantly at the beginning of the twentieth century as a result of human exploitation (e.g. Heupink, van den Hoff, & Lambert, Reference Heupink, van den Hoff and Lambert2012; Rounsevell & Copson, Reference Rounsevell and Copson1982). Recently, the global population has begun to stabilise, and some populations appear to be increasing (Bost et al., Reference Bost, Delord, Barbraud, Cherel, Pütz, Cotté, Weimerskirch, Borboroglu and Boersma2013). In some of its former range, the species has returned to areas from which it had disappeared, e.g. on the Falkland Islands (Otley, Clausen, Christie, Huin, & Pütz, Reference Otley, Clausen, Christie, Huin and Pütz2007; Pistorius et al., Reference Pistorius, Baylis, Crofts and Pütz2012) and Heard Island (Budd & Downes, Reference Budd and Downes1965; Gales & Pemberton, Reference Gales and Pemberton1988). Single incubating pairs were found on the South Sandwich Islands in 1995 and 1997; however, no chicks were reported (Convey, Morton, & Poncet, Reference Convey, Morton and Poncet1999; Prince & Croxall, Reference Prince and Croxall1996; Watson, Reference Watson1975).
Furthermore, breeding attempts were recently noted in the South Shetland Islands: on Elephant Island (Petry et al., Reference Petry, Basler, Valls and Kruger2013) and on King George Island (Juáres et al., Reference Juáres, Ferrer, Coria and Santos2017), where an increased number of observations was also reported (Peter, Büsser, Mustafa, & Pfeiffer, Reference Peter, Büsser, Mustafa and Pfeiffer2008; Peter et al., Reference Peter, Braun, Janowski, Nordt, Nordt and Stelter2013). Here we report the establishment of a new king penguin breeding site, the third for the South Shetlands and the second for King George Island. The site is situated at Lions Rump (62°8′2′′S, 58°7′26′′W) among a large colony of Adélie penguins (Pygoscelis adeliae). This is the first documented example of king penguins breeding in an Adélie penguin colony.
Methods
Observations were made in two Antarctic Specially Protected Areas at King George Island: Western Shore of Admiralty Bay (ASPA 128) and Lions Rump, Western Shore of King George Bay (ASPA 151). King George Island is situated approximately 125 km north from the tip of the Antarctic Peninsula (Figs 1 & 2). Admiralty Bay (AB) is an ice-free area of approximately 16.8 km2 (ATCM, 2014). Since 1977, this area has been the site of continuous, year-round monitoring of bird and pinniped populations. Lions Rump, hereafter LR, covers an area of approximately 1.3 km2 along the western coastline of King George Bay (ATCM, 2013). In 2007, sporadic observations were replaced here by systematic daily monitoring during the Antarctic summer (from the beginning of November to the end of March) in the years 2007–2017.
Breeding sites and at-sea range (BirdLife International and Handbook of the Birds of the World, 2016) of king penguins in the southern Atlantic Ocean and new breeding sites in the Antarctic Peninsula region, based on published data (Convey et al., Reference Convey, Morton and Poncet1999; Juáres et al., Reference Juáres, Negrete, Mennucci, Perchivale, Santos, Moreira and Coria2014, Reference Juáres, Ferrer, Coria and Santos2017; Petry et al., Reference Petry, Basler, Valls and Kruger2013; Pütz et al., Reference Pütz, Trathan, Pedrana, Collins, Poncet and Lüthi2014) and this study. Locations of the fronts according to Orsi and Harris (Reference Orsi and Harris2001).
Sites of observations and breeding attempts of king penguins on (a) King George Island (South Shetland Islands, Western Antarctic) (Juáres et al., Reference Juáres, Negrete, Mennucci, Perchivale, Santos, Moreira and Coria2014, Reference Juáres, Ferrer, Coria and Santos2017; Lesiński, Reference Lesiński1993; Peter et al., Reference Peter, Büsser, Mustafa and Pfeiffer2008, Reference Peter, Braun, Janowski, Nordt, Nordt and Stelter2013; this study); (b) sites of breeding, moulting and regular observations of king penguin species at Lions Rump (ASPA 151) from 2011 to 2017, among breeding groups of Pygoscelis (from 2014, see also Gryz, Korczak-Abshire, & Gerlée, Reference Gryz, Korczak-Abshire and Gerlée2015).
Both ASPAs are breeding sites of three species of Pygoscelis penguin (Adélie P. adeliae, gentoo P. papua, chinstrap P. antarcticus). There are five penguin breeding colonies in Admiralty Bay (Chwedorzewska & Korczak, Reference Chwedorzewska and Korczak2010; Jabłoński, Reference Jabłoński1986; Korczak-Abshire, Chwedorzewska, Wąsowicz, & Bednarek, Reference Korczak-Abshire, Chwedorzewska, Wąsowicz and Bednarek2012; Sierakowski, Korczak-Abshire, & Jadwiszczak, Reference Sierakowski, Korczak-Abshire and Jadwiszczak2017; Trivelpiece, Trivelpiece, & Volkman, Reference Trivelpiece, Trivelpiece and Volkman1987) and one at Lions Rump (Korczak-Abshire, Węgrzyn, Angiel, & Lisowska, Reference Korczak-Abshire, Węgrzyn, Angiel and Lisowska2013), with a total of 23,840 breeding pairs recorded in 2014 (Zmarz, Korczak-Abshire, Storvold, Rodzewicz, & Kędzierska Reference Zmarz, Korczak-Abshire, Storvold, Rodzewicz and Kędzierska2015). Observations were carried out every 10 days in AB, and daily at LR (from 2007 to 2017). Field work was related to the monitoring of krill-dependent indicator species, and observations were conducted according to the standards of the CCAMLR Ecosystem Monitoring Program (CEMP) of the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR, 2014).
Recent data were collected using Delta Optical Forest II 10 × 42 binoculars, a Canon EOS 7D camera equipped with a Canon EF-S 55–250 mm f / 4.0–5.6 IS lens and a Canon 100–400 mm f/4.5–5.6L IS USM lens. Since 2015, ten camera traps (RECONYX PC800 Hyper Fire Professional Semi-Covert) were used additionally to monitor penguin populations at Lions Rump.
Abandoned eggs were weighed and measured with a Pesola Medio line weight scale (300 g/2 g), and Digital Vorel Calipers (150 mm/0.01 mm). Locations of individual king penguins (both breeding and non-breeding) observed at LR since 2007 were recorded using a hand-held GPS (Magellan Mobile Mapper). The summarised data were analysed (ESRI® ArcMAP™ 10.0 software) and used to develop a detailed map (Fig. 2b). Here, “record” means an observation of one or more individuals on a given day at a given location in AB or at LR. If one or more birds were observed several times on the same day in the same location, all those observations were treated as a single record. When birds were observed on the same day and at the same time in both study areas, AB and LR, the sightings were treated as two separate records. However, it should be noted that no bird was banded.
Results
Records of king penguins in Admiralty Bay and at Lions Rump in the period from 1977 to 2017 were based on original field observations, published data and confirmed personal communications (Tables 1 & 2; Figs 2 & 3). From 1977 to 2004 only two individuals were observed, one in AB (Lesiński, Reference Lesiński1993) and one (moulting) at LR in 1991 (A. Gaździcki, personal communication, 4 July 2018). In February 2005, a moulting king penguin stayed in the vicinity of the Polish Arctowski Station (Admiralty Bay) for almost a month (A. Kidawa and A. Nędzarek, personal communication, 25 August 2014). At LR, the species was first seen in 1991, and since 2007 the number of observations has increased (Table 1). During 2005–2017, king penguins were observed 565 times in total in both study areas; 509 of those observations were made in the LR area. Most observations were related to breeding attempts in the last four seasons, from 2013/2014 to 2016/2017 (Table 2; Fig. 4). A single king penguin was also recorded at Aitcho Islands (South Shetland Islands) on 5 December 2007 (T. Łękarski, personal communication, 22 June 2018) and at Cape Melville (King George Island) on 2 February 2011 (Table 1). From the start of the 2010/11 season to the end of the 2016/17 season, king penguins were recorded regularly, and were observed every year in both study areas. The number of records increased with each successive season (except season 2016/17, see Table 1). The number of birds sighted at the same time also increased since the beginning of the 2010/11 season. In total, more than one individual was seen during 108 observations.
Number of records of king penguins in ASPAs 128 (AB) and 151 (LR) per month, based on published data, confirmed personal communications, and present study observations in the period 1977–2017. It should be noted that during winter (April–November) in 2016 data were recorded by camera traps, which did not cover the entire area of Lions Rump.
Example images of breeding attempts of king penguins in an Adélie penguin breeding colony at Lions Rump (ASPA 151) during different Antarctic summers: (a) individual in the largest Adélie penguin breeding group, 28 November 2013; (b) king penguin pair courting in the same largest Adélie penguin breeding group, 5 December 2013; (c) incubating individual, 28 February 2014; (d) incubating individual, 18 January 2015; (e) single king penguin in Adélie penguin breeding group, 8 January 2015; (f) king penguin pair among incubating Adélie penguins, 25 November 2014; (g) incubating individual, 2 March 2015; (h) incubating individual, with a previously abandoned egg visible, 11 December 2014; (i) individual and an abandoned egg, 27 December 2016 (photography by A. Gasek, P. Gryz, A. Grebieniow).
Records of individual king penguins in Admiralty Bay (ASPA 128) and at Lions Rump (ASPA 151), King George Island from 1977 to 2017, based on Lesiński (Reference Lesiński1993) and original field observations.
Comments: during the seasons 2013/14, 2015/16 and 2016/17 a total of 29 days were not recorded. However, the authors assume that at least one bird was present in the investigated area, as it was incubating and moulting time in all cases.
Dates of king penguin breeding attempts observed at King George Island in 2011–2017 (marked in grey) at Stranger Point (62°16′S, 58°37′W) based on Juáres et al. (Reference Juáres, Ferrer, Coria and Santos2017) and (marked in white) at Lions Rump (ASPA 151) (this study).
* In the case of data from Stranger Point, dates of first and last records of the egg and chick, respectively (see Table 1, Juarez et al., Reference Juáres, Ferrer, Coria and Santos2017).
** 23 Dec 2015: no observation was carried out on that day, and therefore the exact date of laying of the second egg is unknown.
*** Refers to the second egg that has not been abandoned and which birds have been incubating, respectively.
**** In the season 2015/16, Reconyx photo cameras have been installed and allowed for extending observations during winter.
NO: not observed; the event did not take place during the period of observation.
UKN: unknown.
Over the last several decades, nearly all the records were obtained during the Antarctic summer, especially in December (AB), January and February (LR) (Fig. 3). In other months, birds appeared less frequently (Fig. 3). However, images obtained from the camera traps proved that king penguins visited at LR in May, June and August (Figs 3 & 5).
Two king penguins in an image obtained from a camera trap (RECONYX PC800 Hyper Fire Professional Semi-Covert) on 5 June 2016, Lions Rump, King George Island, South Shetlands.
Moulting penguins were recorded five times at LR, once in 1991 and four times from 2013/14 to 2016/17 (Fig. 6; Table 1); and once in February 2005 in AB, near Arctowski Station. Most moulting king penguins at LR were sighted in October and November (Fig. 3). It is likely that the same birds stayed at LR throughout the entire summer season, after undergoing the moult (probably pre-nuptial). The exception was in the 2016/17 season, when one individual was recorded in January (Fig. 3; Table 2). Details of king penguin breeding attempts and the chronology at King George Island are summarised in Table 2. The first breeding attempt was observed at Stranger Point (62°16′S, 58°37′W) in 2011/2012 and further breeding attempts were noted there each year until 2014/2015 (Juáres et al., Reference Juáres, Negrete, Mennucci, Perchivale, Santos, Moreira and Coria2014, Reference Juáres, Ferrer, Coria and Santos2017). Although no breeding attempts were observed at Lions Rump in the 2011/2012 season, single adult birds were recorded occasionally between 25 November and 6 March. A similar situation was observed in the subsequent season of 2012/2013; however, a case of permanent stay of one individual was recorded during the first two weeks of February. On 6 and 7 February 2013 an uncommon observation was documented. This single adult king penguin was feeding, nurturing and cleaning the plumage of older gentoo penguin chicks (Fig. 7). On 7 February the king penguin was observed interacting aggressively with adult gentoo penguins, evidently trying to take over chicks. The first breeding attempt and observation of an incubating king penguin pair at Lions Rump took place in the next season 2013/2014. Subsequently, breeding attempts occurred every year until the 2016/2017 season. The same events occurred in the first three seasons from 2013/2014 to 2015/2016 (Table 2). Each year, after the pre-nuptial moult (October–November), a pair courted in November–December, laid an egg in December, but abandoned the egg after one, ten or nine days, respectively. Another egg was laid on the same day of abandonment, except in 2013/2014, when a second egg was laid 54 days after the first one was abandoned. It is not clear whether it was a new pair or the same pair of birds that re-laid in this case. At LR, a maximum of three birds were sighted simultaneously on four occasions (first on 29 January 2015).
Example images of moulting king penguins. Images were taken at: (a) AB on 17 February 2005, (b) LR on 22 February 1991, (c) LR on 25 October 2014, and (d) LR on 18 January 2017 (photography by A. Nędzarek, A. Gaździcki, P. Gryz, A. Grebieniow).
Adult king penguin protecting chick of gentoo penguin, observed in the 2012/2013 season at LR (photography by P. Gryz).
In summary, at least two pairs incubated simultaneously at two sites at Strange Point (Juáres et al., Reference Juáres, Negrete, Mennucci, Perchivale, Santos, Moreira and Coria2014, Reference Juáres, Ferrer, Coria and Santos2017) and at LR in two seasons: 2013/2014 and 2014/2015. At LR, two eggs were laid in each season except in 2016/2017, when just one egg was observed on 25 December, which was abandoned after two days. During this season there were no more breeding attempts, although birds (single or pairs) were seen from 7 January to 19 March.
At LR in 2013/14 one chick hatched, which was subsequently found dead on 9 April 2014 (no photo documentation). Cases of prolonged incubation of the second egg, exceeding the estimated time to hatching (54–55 days, Stonehouse, Reference Stonehouse1960) were observed in seasons 2014/15 (>88 days) and 2015/16 (>97 days). Egg shells covered by thick layers of guano and mud were noted, indicating occasions of unsuccessful egg transfer; such transfers were observed four times and eggs were later abandoned (Fig. 4h, i).
Discussion
The first historical records of king penguins at the South Shetland Islands come from accounts by nineteenth century explorers, who also mention breeding attempts of this species in the archipelago (Eights, Reference Eights1833; Fildes, Reference Fildes1821), although those were questioned by Conroy and White (Reference Conroy and White1973). For the period 1970–2004 there are just a few documented records of king penguins in the South Shetland Islands: on Elephant Island (Furse & Bruce, Reference Furse and Bruce1975; Petry et al., Reference Petry, Basler, Valls and Kruger2013), Nelson Island (Lumpe & Weidinger, Reference Lumpe and Weidinger2000), and King George Island (Lesiński, Reference Lesiński1993; Peter et al., Reference Peter, Büsser, Mustafa and Pfeiffer2008, Reference Peter, Braun, Janowski, Nordt, Nordt and Stelter2013). This small number of observations of king penguins in the South Shetland Islands region may have been the result of (1) less intensive observational efforts by researchers, (2) gaps in reporting, (3) low ‘pressure’ of the depleted population for finding new breeding sites, as a result of human exploitation at the beginning of the twentieth century, or (4) climate change. Analyses of ice cores from James Ross Island (64°10′S, 57°45′W) at the eastern side of the Antarctic Peninsula indicate that in the mid-nineteenth century air temperatures may have been up to 2°C higher than in the 1990s, with the warmest period occurring ca. 1850 (Aristarain, Jouzel, & Lorius, Reference Aristarain, Jouzel and Lorius1990). It is therefore possible that, in a milder climate, king penguins attempted to breed at the South Shetland Islands, but probably infrequently. Cooler conditions from 1850 to 1930 and prominent warming since 1950 were reported by Thompson et al. (Reference Thompson, Peel, Mosley-Thompson, Mulvaney, Dai, Lin and Raymond1994), who analysed ice cores from the Dyer Plateau (70°30′S, 65°0′W). Since the mid-twentieth century, the Antarctic Peninsula region has been warming faster than any other Southern Hemisphere region (e.g. Kejna, Reference Kejna1999, Reference Kejna2003; Kejna, Araźny, & Sobota, Reference Kejna, Araźny and Sobota2013; Steig et al., Reference Steig, Schneider, Rutherford, Mann, Comiso and Shindell2009; Turner et al., Reference Turner, Colwell, Marshall, Lachlan-Cope, Carleton, Jones and Iagovkina2005). Wildlife responses to this phenomenon have already been described (e.g. Galera, Chwedorzewska, Korczak-Abshire, & Wódkiewicz, Reference Galera, Chwedorzewska, Korczak-Abshire and Wódkiewicz2018; Hinke, Salwicka, Trivelpiece, Watters, & Trivelpiece, Reference Hinke, Salwicka, Trivelpiece, Watters and Trivelpiece2007; Korczak-Abshire, Angiel, & Wierzbicki, Reference Korczak-Abshire, Angiel and Wierzbicki2011; Trathan et al., Reference Trathan, García-Borboroglu, Boersma, Bost, Crawford, Crossin and Wienecke2015). In particular, king penguins are predicted to have to shift their foraging ranges further south in response to warming conditions (Cristofari et al., Reference Cristofari, Liu, Bonadonna, Cherel, Pistorius, Le Maho and Trucchi2018; Péron, Weimerskirch & Bost, Reference Péron, Weimerskirch and Bost2012). A similar suggestion was made for pinnipeds, especially for southern elephant seals (McIntyre et al., Reference McIntyre, Ansorge, Bornemann, Plötz, Tosh and Bester2011), another species that has started showing signs of increasing presence further south (Gil-Delgado et al., Reference Gil-Delgado, Villaescusa, Diazmacip, Velazquez, Rico, Toro, Quesada and Camacho2013).
The changing environment may lead to attempts to colonise the South Shetland Islands. An increase in sea surface temperatures has a negative impact on king penguins, as it causes a shift in the southern range of their prey (Hobday, Reference Hobday2010; Péron et al., Reference Péron, Weimerskirch and Bost2012). The need to forage further south may also drive the extension of the range of this species.
The exact number of king penguins currently visiting the South Shetlands is unknown; however, observations at Stranger Point (Juáres et al., Reference Juáres, Negrete, Mennucci, Perchivale, Santos, Moreira and Coria2014, Reference Juáres, Ferrer, Coria and Santos2017), Elephant Island (Petry et al., Reference Petry, Basler, Valls and Kruger2013), the Fildes Peninsula (Peter et al., Reference Peter, Büsser, Mustafa and Pfeiffer2008, Reference Peter, Braun, Janowski, Nordt, Nordt and Stelter2013) and those presented here attest that the archipelago is visited by king penguins regularly. Since 2004, observations of king penguins at King George Island have been frequent and their number has been increasing since 2011 (Table 1). In addition, there appear to be unpublished observations of king penguins at other islands of the archipelago, for example at Aitcho Islands (T. Łękarski, personal communication, 22 June 2018). Furthermore, several (up to three) individuals were observed simultaneously at the same location on several occasions (e.g. three birds were seen four times at LR in the summer season 2015/16). In addition, in the years 2005–2012 an increased number of observations were made on the Potter Peninsula and at Ardley Island, where up to three live birds and five dead individuals were found at the same time twice (Peter et al., Reference Peter, Büsser, Mustafa and Pfeiffer2008, Reference Peter, Braun, Janowski, Nordt, Nordt and Stelter2013).
During at least two summer seasons (2013/2014 and 2014/2015), king penguins attempted to breed in two different locations, Lions Rump and Stranger Point, at King George Island. At Stranger Point, a chick hatched on 5 February 2015 and remained alive for 5 months (Juáres et al., Reference Juáres, Ferrer, Coria and Santos2017). So far this is the only report of a live king penguin chick at the South Shetlands. According to Stonehouse (Reference Stonehouse1960) three breeding statuses are recognised: early, late and ineffective breeders. Late breeders may leave their eggs or small chicks early in May, while winter drifts appear in the colony. Van den Hoff, McMahon, and Field (Reference Van den Hoff, McMahon and Field2009), describing the timing of breeding events in a re-established colony of king penguins at Macquarie Island (54°37′S, 158°51′E), also noticed breeding failure in the case of late breeders. In the case of early breeders, chicks hatched by 5 February were successfully reared to fledging by 16 October. However, Macquarie Island is an established breeding site of king penguins in the sub-Antarctic region.
King penguins also visited LR, the new breeding sites during winter, e.g. in June 2016 (Fig. 5). AB and LR were visited by a pair of king penguins five times during May–August (Fig. 3). These visits took place in 2015/2016 after an unsuccessful and prolonged incubation period (until April) at Lions Rump. Additionally, a seriously wounded immature individual was observed on 24 May 2016 in AB. Observations of unsuccessful egg transfers, egg abandonment (<55 days post laying), and prolonged incubation (>55 days; the eggs may not have been fertile) may indicate that the observed penguins were inexperienced breeders (Stonehouse, Reference Stonehouse1960). Moreover, it is not out of the question that other king penguins appeared on the island and some of them disturbed the breeding pairs from Lions Rump and Stranger Point. Stonehouse (Reference Stonehouse1960) reported such a case.
The breeding attempts described here, and the increased number of occurrences at King George Island, may also be due to increases in populations at existing breeding sites, such as South Georgia (e.g. Petry et al., Reference Petry, Basler, Valls and Kruger2013). However, further research is needed to determine the origin of individuals arriving at the South Shetland Islands. Moreover, the size of the global king penguin population fluctuates extensively and several large colonies appear to have decreased (Bost et al., Reference Bost, Delord, Barbraud, Cherel, Pütz, Cotté, Weimerskirch, Borboroglu and Boersma2013), e.g. at Ile aux Cochons, Iles Crozet, in the Indian Ocean (Weimerskirch et al., Reference Weimerskirch, Le Bouard, Ryan and Bost2018).
Clucas et al. (Reference Clucas, Younger, Kao, Rogers, Handley, Miller and Hart2016) examined the genetic population structure and patterns of colonisation of king penguins across their current range and found only slight genetic differentiation among colonies thousands of kilometres apart. These results suggest that migration among islands and archipelagos may be common. Moreover, the results showed that the South Georgia population was slightly different from all other colonies and that the recently founded Falkland Island colony may have been established by migrants from the distant Crozet Islands rather than nearby colonies at South Georgia (Clucas et al., Reference Clucas, Younger, Kao, Rogers, Handley, Miller and Hart2016).
The high dispersal ability of king penguins implies that new locations may be colonised rapidly. Cristofari et al. (Reference Cristofari, Liu, Bonadonna, Cherel, Pistorius, Le Maho and Trucchi2018) suggested some conditions that must be met for an island to be colonised, including the following: islands must be (1) predator free, ice free, and reasonably flat, (2) with sites within the maximum foraging distance to the prey stock (crucial during offspring nourishing), and (3) have low sea-ice concentrations during winter. If recent climate change trends in the Western Antarctic Peninsula (WAP) region continue, locations such as the South Shetlands may become more suitable for king penguins in the future. Moreover, the establishment of new breeding sites along the WAP and southern range extension related to recent climate warming has already been reported for other penguin species, such as gentoo (Pygoscelis papua) and chinstrap (Pygoscelis antarcticus) (e.g. Ducklow et al., Reference Ducklow, Baker, Martinson, Quetin, Ross, Smith and Fraser2007; McClintock, Silva-Rodriguez & Fraser, Reference McClintock, Silva-Rodriguez and Fraser2010).
Observations described here confirm the predictions of other authors (Juáres et al., Reference Juáres, Ferrer, Coria and Santos2017; Petry et al., Reference Petry, Basler, Valls and Kruger2013), who suggested the possibility of further breeding attempts by king penguins in the region of the South Shetland Islands. If climate warming in the Antarctic Peninsula region continues, further growth of the population of this species in the Antarctic can be expected, as well as breeding attempts at other sites located even further south.
Author ORCIDs
Alina Gerlée 0000-0002-2123-7336; Małgorzata Korczak-Abshire 0000-0001-7695-0588
Acknowledgments
Gracious thanks to Drs Wiesława Misiak, Marco Favero and Marek Kejna for constructive comments during manuscript preparation and proofreading. The authors would also like to thank Mrs Żaneta Bartosińska for assistance with the reference collection, and all the Polish Antarctic Programme members who, often with great sacrifice, conducted field observations of this species: A. Gasek, A. Grabieniow, Prof. A. Gaździcki, A. Kidawa, A. Nędzarek, T. Łękarski, P. Angiel, A. Barcikowski, A. Body, J. Czarnul, J. Dzido, M. Figielski, S. Gleich, D. Górniak, P. Horzela, B. Jerzak, P. Kapuściński, J. Kończak, A. Latusek, E. Libera, R. Łabno, T. Mieczan, J. Piszczek, I. Sobota, M. Świetlik, L. Urbański and M. Witczak. We thank the anonymous reviewers for their friendly and constructive criticism and remarks, which have greatly improved our manuscript. This research was partially financed by the Polish–Norwegian Research Programme operated by the National Centre for Research and Development under the Norwegian Financial Mechanism 2009–2014 in the frame of Project Contract No. 197810. Hardware, RECONYX PC800 Hyper Fire Professional Semi-Covert Cameras, was funded with the generous support of the CCAMLR (Commission for the Conservation of Antarctic Marine Living Resources) Ecosystem Monitoring Program Special Fund. The data used in the paper were collected while based at Henryk Arctowski Polish Antarctic Station.
