Comparison of foraging strategies of incubating king penguins Aptenodytes patagonicus from Macquarie and Heard islands

The foraging strategies of king penguins from Heard and Macquarie islands were compared using satellite telemetry, time-depth recorders and diet samples. Trip durations were 16.8±3.6 days and 14.8±4.1 days at Macquarie and Heard islands, respectively. At Macquarie Island, total distances travelled were 1281±203 km compared to 1425±516 km at Heard Island. The total time the penguins spent at sea was 393±66 h at Macquarie Island and 369±108 h at Heard Island. The penguins from Macquarie Island performed more deep dives than those from Heard Island. King penguins from Macquarie Island travelled 1.5±0.2 km h⁻¹ day⁻¹ compared to 1.3±0.1 km h⁻¹ day⁻¹. At Macquarie Island, 19% of dives were upto 70–90 m depth compared to 35% at Heard Island. The main dietary prey species were the fish Krefftychthis anderssoni and the squid Moroteuthis ingens in both groups. The differences in the at-sea distribution and the foraging behaviour of the two groups of penguins were possibly related to differences in oceanography and bathymetric conditions around the two islands. Dietary differences may be due to interannual variability in prey availability since the two colonies were studied during incubation but in different years.     

Movements of foraging king penguins through marine mesoscale eddies

Despite increasing evidence that marine predators associate with mesoscale eddies, how these marine features influence foraging movements is still unclear. This study investigates the relationship of at-sea movements of king penguins to mesoscale eddies using oceanographic remote sensing and movement data from 43 individual trips over 4 years. Simultaneous satellite measurements provided information on gradients of sea surface temperature and currents associated with eddies determined from altimetry. Penguins tended to swim rapidly with currents as they travelled towards foraging zones. Swimming speed indicative of foraging occurred within mesoscale fronts and strong currents associated with eddies at the Polar Front. These results demonstrate the importance of mesoscale eddies in directing foraging efforts to allow predators to rapidly get to rich areas where high concentrations of prey are likely to be encountered. When returning to the colony to relieve the incubating partner or to feed the chick, the birds followed a direct and rapid path, seemingly ignoring currents.     

Foraging range of king penguins Aptenodytes patagonicm during summer at Marion Island

Foraging ranges of king penguins Aptenodytes patagonicus were estimated by combining information on the feeding rates to chicks and brood shift lengths of adults (assessed by daily weighings of large chicks and daily checks of marked birds brooding small chicks) with measurements of travelling speeds and activity budgets at sea (assessed using remote recording devices). Adults brooding small chicks were relieved on average every 13 days and large chicks were fed every four days. Adults with large chicks spent 36% of their time, between attachment of the device and recapture, travelling at an average speed of 8.7 km.h^-1. This gives an estimated mean maximum foraging range of about 300 km. Adults attending small chicks spent 19% of their time away swimming, giving an estimated mean maximum foraging range of 225 km. Extreme foraging ranges for all birds were 75 and 902 km for penguins returning between two and 24 days at sea, respectively. Total distance travelled was highly correlated with time away from the colony.     

New southerly breeding location of king penguins (Aptenodytes patagonicus) on Elephant Island (Maritime Antarctic)

In the 2009–2010 austral summer, two breeding pairs of king penguins were recorded at Stinker Point, Elephant Island, Maritime Antarctic. This is the first record of king penguins breeding south of 60°S. The finding suggests a possible range extension of this species and increases the number of breeding bird species at Stinker Point, which was recently appointed as an Important Bird Area in Antarctica.     

Behavioural time budget of breeding king penguins (Aptenodytes patagonica)

As do so many other seabirds, penguins fast when ashore for breeding. For penguins in dense colonies, territory defence seems to imply conflicting energetic requirements because of its assumed high energy cost, when the birds need to limit energy expenditure to cope with their fast. In this context, behavioural time budget over 24 h was investigated during breeding in the king penguin, Aptenodytes putugonicu , by using a remote-controlled videocamera. The comparison of day-night activity was performed in relation to breeding status (incubation vs. brooding) and duration of fasting (beginning vs. end of incubation shift). Five categories of behaviours were quantified: territoly defence, comfort, resting, sleeping and chick-feeding. Breeding king penguins remain active by day as well as by night. Between incubation and brooding we found a three-fold increase in the energy consuming temtory defence, together with a drastic decrease in that posture which corresponds to deep sleep, is. when most energy is saved. These increases in aggressiveness and vigilance may be related to protection of the newly hatched chick. Between the onset and the end of an incubation shift, the time spent in sleep increases three-fold, whereas territory defence remains unchanged. These data for penguins under natural conditions accord with previous studies on captive birds which have shown that an increasing proportion of sleep during the course of fasting may contribute to energy saving. On the other hand, both resting (which is the main component of penguins'time budget; about 65%) and comfort (about 16% of time) show no change either between incubation and brooding or during the course of fasting.     

Maximum diving depths of northern rockhopper penguins (Eudyptes chrysocome moseleyi) at Amsterdam Island

 The mean maximum dive depth from 49 foraging bouts by northern rockhopper penguins, measured using capillary-tube depth gauges, was 66±4 m (12–168 m). There were no differences in the maximum dive depths between male and female penguins. Northern rockhopper penguins dived deeper in early than in late creche stages (83±7 vs 57±4 m), and this was associated with probable dietary changes, squid dominating the diet by mass (44%) in November, and fish (64%) in December 1994 at Amsterdam Island. Received: 10 January 1996/Accepted: 31 March 1996     

Population status and breeding season chronology of Heard Island fur seals

Fur seals were eliminated by sealers at Heard Island soon after its discovery in the 1850s. The first recorded breeding of Antarctic fur seals (Arctocephalus gazella) since sealing was reported in early 1963 (two pups). The most recent survey of the Heard Island fur-seal population was undertaken between November 2000 and March 2001, when 1,012 Antarctic fur-seal pups were born. This represents a fourfold increase since the last complete census in 1987/1988 (13 years), when 248 births were recorded. Pup estimates and counts available for eight breeding seasons since 1962/1963 suggest the population has been increasing at between 12 and 20% per year. Based on pup production, the breeding population is estimated to number approximately 4,100 seals. The number of fur seals on Heard Island peaked in late February/early March at 29,256 indicating that, in addition to the breeding population, a significant number of seals born elsewhere haul out on the island. Most of these are moulting sub-adult and adult males. As in 1987/1988, only one subantarctic fur-seal pup (A. tropicalis) was observed, suggesting this species is not colonising the island, as has been speculated.     

Seasonal variation in the diet of the king penguin (Aptenodytes patagonicus) at sub-Antarctic Marion Island

King penguins are important consumers of marine resources, throughout the year, at the Prince Edward Islands. Meal size varied from 8.5–12.6% of adult mass, depending on the method of determination. In spite of the biases in the analysis favouring the overestimation of squid, fish and, in particular, myctophid fish accounted for the largest proportion of the stomach samples, 87% by wet mass, 75% by numbers and 69% by reconstituted mass. The relative abundance of fish in the diet dropped markedly in winter followed by a subsequent rise to nearly 100% in summer. This rise coincided with an increase in the chick growth rate and the king penguin population at the island and suggests the rise in relative abundance offish reflects a real increase in the availability of fish around the islands.
Juvenile and adult Krefftichthys anderssoni/Protomyctophum tenisoni and adult Electrona carlsbergi were the most common fish consumed. There was an increase in the modal size of K. anderssoni/P. tenisoni throughout the year which we interpret as growth of a single fish population. Juvenile Kondakoviu longimana was the important squid species taken by king penguins. Crustaceans were only rarely recorded in the diet and may have come from digestion of fish and squid stomachs.
This is the first study of the diet of a Southern Ocean pelagic predator that has identified myctophid fish as a major component of its diet. All three important fish species taken by king penguins at Marion Island have a wide distribution throughout the Southern Ocean and consequently may prove to be important dietary components of other Southern Ocean pelagic predators.     

Population dynamics in a long-lived seabird: I. Impact of breeding activity on survival and breeding probability in unbanded king penguins

Understanding the trade-off between current reproductive effort, future survival and future breeding attempts is crucial for demographic analyses and life history studies. We investigated this trade-off in a population of king penguins (Aptenodytes patagonicus) marked individually with transponders using multistate capture-recapture models. This colonial seabird species has a low annual proportion of non-breeders (13%), despite a breeding cycle which lasts over 1 year. To draw inferences about the consequences of non-breeding, we tested for an effect of reproductive activity on survival and on the probability of subsequent breeding. We found that birds non-breeding in year t show the same survival rate as breeders (two-states analysis: breeding and non-breeding). However, breeders had a lower probability of breeding again the following year. This negative phenotypic correlation suggests the existence of reproductive costs affecting future breeding probability, but it might also be strengthened by late arrival for courtship in year t. A three-state analysis including breeding success revealed that failed breeders in year t have a lower probability to reproduce successfully in year t + 1 than non-breeders in year t, providing some evidence for the existence of reproductive costs. Moreover, successful breeders showed higher survival probability. This positive phenotypic correlation between current reproduction and subsequent survival supports the hypothesis of an heterogeneity in individual quality. Males breeding in year t had a lower probability to breed again in year t + 1 than females, suggesting higher reproductive costs for this sex. Such additional costs might be due to higher male parental investment in the final phase of chick-rearing, which also delays the arrival of males in year t + 1, and decreases their breeding probability. Our study is the first to explore the breeding biology and the demography of penguins without the disturbance of flipper-bands.     

Annual variation in breeding biology of macaroni penguins, Eudyptes chvysolophus, at Bird Island, South Georgia

The breeding biology of the macaroni penguin, Eudyptes chrysolophus , was studied over four years, 1976 and 1986–88, at Bird Island, South Georgia. Birds were migratory, being absent during winter (May to September). Arrival at the colony was highly synchronous between years: 14–23 October, over a 7-year period. The pre-breeding, incubation and chick-brooding period was characterized by long fasts ashore, for 36 and 39 days in males and 41 days in females, alternating with long periods at sea. Within years egg-laying was highly synchronous: 95% of clutches initiated within 4–6 days. Arrival date and mean egg-laying date were later (by 3 days), and breeding population size lower (by 20%) in 1987, compared to other years. The incubation period was 35 days and comprised three long shifts, the first shared by the male and female, the second by the female and the third by the male. In 1986 and 1988 these were of 12, 12 and 9 days' duration, but in 1987 the first shift was significantly shorter: 9 days. Chicks creched at 23–25 days of age and fledged at 60 days of age. Neither chick age nor weight at creching or fledging varied between the years 1986–88. The breeding biology of macaroni penguins at Bird Island is compared with that of other Eudyptes penguins, and with the sympatric gentoo penguin, Pygoscelispupuu. There is little variation in breeding biology within the genus Eudyptes , except in the length of time spent at sea prior to the annual moult. This is much shorter at Bird Island, probably reflecting a greater food availability compared to other localities. Inter-annual variation in certain breeding parameters, e.g. laying date, breeding population size, is much greater in the gentoo penguin than in the macaroni penguin. The shorter breeding season, rearing of only one chick and proportionately lower chick fledging weight in macaroni penguins, may be linked to this species' migratory strategy.     

Nutrient reserve storage,energetics, and food consumption during the prebreeding and premoulting foraging periods of king penguins

Nutrient reserve storage during the prefasting foraging trips of king penguins Aptenodytes patagonicus was investigated by measuring body composition at the beginning and the end of the prebreeding and premoulting periods at sea. Both periods were marked by a 45–47% increase in body mass (4.6 and 5.6 kg during the prebreeding and premoulting trips, respectively) including body water (31% and 55% of the total increase in body mass), protein (13% and 16%) and lipid (46% and 23%), but not ash. Fat accretion accounted for most of the energy stored (86% and 71% versus 14% and 29% for protein) and it was mainly located in the subdermal depot, the larger increase in body protein occurring in pectoral muscles. Daily mass gain was lower during the prebreeding foraging trip than during the premoulting one (195 versus 328 g/day), while there was no difference in the rate of energy storage (4,097 and 4,155 kJ/day). The total energy costs of the foraging periods were calculated to be 381 and 315 MJ during the prebreeding and premoulting trips respectively, which corresponded to a 70-kg and a 58-kg food intake. The consumption of marine resources by the king penguin population from Crozet Islands was estimated to be 166,000 tons in spring/summer during the two foraging periods preceding long-term fasts.     

Stable isotopes in southern rockhopper penguins: foraging areas and sexual differences in the non-breeding period

Southern rockhopper penguins (Eudyptes chrysocome chrysocome) have experienced severe population declines across their distribution area, potentially in response to bottom-up effects following elevated sea surface temperatures, changes in the food web and prey availability. We conducted stable isotope analysis to compare trophic levels and distribution patterns in the non-breeding period over three consecutive years, and between males and females, using egg membranes, blood cells and feathers of parent birds. Tissues representing the non-breeding season had lower ??¹³C values than prey sampled around the Falklands and red blood cells from breeding rockhopper penguins. In contrast, ??¹⁵N values were higher in red blood cells from the end of winter compared to those from the breeding season and compared to feathers. This indicated that rockhopper penguins left the Falkland Island area in the non-breeding season and foraged either around Burdwood Bank further south, or over the Patagonian Shelf. In winter, only males took more prey of higher trophic level than females. Inter-annual differences in isotopic values partly correlated with sea surface temperatures. However, as prey isotope samples were collected only in 1?year, inter-annual differences in penguin isotopic values may result from different foraging sites, different prey choice or different isotopic baseline values. Our study highlights the potential for stable isotope analyses to detect seasonal and gender-specific differences in foraging areas and trophic levels, while stressing the need for more sampling of isotopic baseline data.     

First direct, site-wide penguin survey at Deception Island, Antarctica, suggests significant declines in breeding chinstrap penguins

Deception Island (62°57′S, 60°38′W) is one of the most frequently visited locations in Antarctica, prompting speculation that tourism may have a negative impact on the island’s breeding chinstrap penguins (Pygoscelis antarctica). Discussions regarding appropriate management of Deception Island and its largest penguin colony at Baily Head have thus far operated in the absence of concrete information regarding the current size of the penguin population at Deception Island or long-term changes in abundance. In the first ever field census of individual penguin nests at Deception Island (December 2–14, 2011), we find 79,849 breeding pairs of chinstrap penguins, including 50,408 breeding pairs at Baily Head and 19,177 breeding pairs at Vapour Col. Our field census, combined with a simulation designed to capture uncertainty in an earlier population estimate by Shuford and Spear (Br Antarct Surv Bull 81:19–30, 1988), suggests a significant (>50?%) decline in the abundance of chinstraps breeding at Baily Head since 1986/1987. A comparative analysis of high-resolution satellite imagery for the 2002/2003 and the 2009/2010 seasons suggests a 39?% (95th percentile CI?=?6–71?%) decline (from 85,473?±?23,352 to 52,372?±?14,309 breeding pairs) over that 7-year period and provides independent confirmation of population decline in the abundance of breeding chinstrap penguins at Baily Head. The decline in chinstrap penguins at Baily Head is consistent with declines in this species throughout the region, including sites that receive little or no tourism; as a consequence of regional environmental changes that currently represent the dominant influence on penguin dynamics, we cannot ascribe any direct link between chinstrap declines and tourism from this study.     

Diving patterns of female macaroni penguins breeding on Marion Island, South Africa

Despite the large biomass of macaroni penguins Eudyptes chrysolophus in the Southern Ocean, their feeding ecology is poorly known at some important breeding localities. We investigated the diving behaviour and diet of female macaroni penguins feeding small chicks on Marion Island (46o52′S, 37o5′E), South Africa, one of the species’ most northerly breeding sites, supporting 4% of their global population. We then compared our results with similar studies from other localities. In December 2008, we collected information on 12 foraging trips from 6 individuals using time-depth recorders, as well as diet from 42 individuals. Median trip duration was 22.8 h (5.6–80.8 h). Penguins performed 42.8 ± 15.9 dives per hour at sea, with dive depths averaging 24.6 ± 8.6 m and lasting 40.8 ± 12.1 s, although 74.3% of dives were <10 m. Euphasids dominated their diet (86% by mass), mainly Thysanoessa vicina. A second peak in dive depths at 55–80 m might reflect the 12% of fish in their diet. The substantial proportion of shallow night dives (30% of total dives) suggests some foraging occurs at night. Differences in diving patterns of individual macaroni penguins in this study confirmed the behavioural flexibility of these birds reported from other breeding localities. However, most other studies assumed that dives <3–5 m were commuting dives whereas our study suggests that at least some prey are caught during shallow dives. We highlight how different analytical methods can change the outcome of studies. Despite macaroni penguins’ apparent flexibility in foraging behaviour during the breeding season, their numbers are decreasing globally. Further investigations of their foraging behaviour are needed to assess potential competition with other predators and krill fisheries.     

Foraging parameters of gentoo penguins Pygoscelis papua at Marion Island

Summary We measured the foraging parameters of breeding gentoo penguins Pygoscelis papua at sub-Antarctic Marion Island. Mean swimming speed was 7.9 km h^-1. Penguins spent on average 8.1 h away from the colony if they returned on the same day they left and 23.7 h away if they remained at sea overnight. Sixteen percent of the total time away at sea was spent swimming. Time spent swimming, and consequently distance travelled, during a foraging trip were highly variable and showed significant intercolony differences. However, 80% of all foraging trips totalled less than 40 km. Meal sizes were small and there was no correlation between meal size and distance travelled, suggesting a low availability of food. Prey items in the diet consisted mainly of the benthic shrimp Nauticaris marionis and the demersal fish Notothenia squamifrons. On evidence from stomach contents and the distances the penguins travelled, we suggest that Nauticaris marionis has a more restricted distribution around Marion Island than does Notothenia squamifrons. The concentration of gentoo penguin breeding colonies along the east coast of Marion Island and the south-east coast of Prince Edward Island may be attributable to favourable feeding conditions between the two islands.     

Breeding energetics and food requirements of gentoo penguins (Pygoscelis papua) at Heard and Macquarie Islands

The food and energy requirements of breeding gentoo penguins ( Pygoscelis papua ) were studied at Heard and Macquaric Islands by means of isotope turnover techniques.
The food consumption rates of chicks were measured at various stages of growth, providing estimates of the total food provided by adults to rear a chick to fledging.
The energy expenditures of attending adults were also measured at different stages of chick-rearing, allowing the total energy costs associated with breeding to be established for a pair of adults and at the population level on both islands. We estimate the total annual energy budget of a 6·2 kg breeding gentoo penguin to be 1517 MJ which is equivalent to the consumption of 292 kg prey.