Annual variation in breeding biology of gentoo penguins, Pygoscelis papua, at Bird Island, South Georgia

The breeding biology of the gentoo penguin, Pygoscelis papua , was studied over a three-year period (1986–1988) at Bird Island, South Georgia, with particular reference to birds of known age or breeding experience. Laying date varied significantly between all three years, being three weeks later in 1987, when the breeding population decreased markedly. Factors involved in the timing of breeding are discussed. Within years egg-laying was highly synchronous: 95% of clutches were initiated in 14·5 days or less. The incubation period was 35 days and the laying interval, between the two eggs, 3·3–3·4 days. Chicks creched when 25–30 days old, and this varied between years, possibly related to food supply and chick growth. Chicks left the colony for the first time between 75 and 85 days of age. The breeding population at Bird Island decreased by 20% and increased by 84% in successive years during the study period. Breeding success (chicks fledged per egg laid) varied between 0·33 and 0·65 within colonies, but for the whole island was very consistent over the three years: 0·45, 0·51 and 0·47. Overall, colony differences were not correlated between years. Disturbance from Antarctic fur seals, Arctocephalus gazella , is suggested as the cause of consistently lower breeding success at one colony. Mean egg weight varied annually, and with age of the breeding bird, nest location and, in one year, with laying date. Young, first-time breeders laid smaller eggs and had lower breeding success compared to older, experienced birds, similar to other seabirds. However, they differed from other species in laying on average earlier than older birds. The relationship between age, egg weight, laying date and breeding success is discussed in relation to predation and seasonal food supply.     

Dietary segregation of krill-eating South Georgia seabirds

The diets of six of the main seabird species (two petrels, two albatrosses, two penguins) breeding at Bird Island, South Georgia were studied simultaneously during the chick-rearing period in 1986. For five species, Antarctic krill Euphausia superba was the main food (39–98% by mass); grey-headed albatrosses took mainly the ommastrephid squid Martialia hyadesi (71%) and only 16% krill. The size of the krill taken was similar between seabird species, although there were small but significant differences between penguins and the other species. Sex and reproductive status of krill, however, was different between all seabird species, reflecting some combination of differences in foraging ranges, selectivity by predators, or differences in escape responses of krill. For the krill-eating species, the rest of the diet varied substantially between species, comprising Martialia and nototheniid fish (blackbrowed albatross and, along with lanternfish, white-chinned petrel), lanternfish and amphipods (Antarctic prion and macaroni penguin), and icefish (gentoo penguin). Long-term data on breeding success and information on diet in 5–10 other years suggest that in 1986 seabird diet and reproductive performance was indicative of a year of good availability of krill around South Georgia. In such circumstances, ecological segregation between krill-eating species appears to be maintained chiefly by differences in foraging range and feeding methods, which are reviewed. This situation is rather different from the few studies of seabird communities elsewhere, where prey type and size are believed to be the main mechanisms of dietary segregation.     

A new high-latitude record for the macaroni penguin (Eudyptes chrysolophus) at Avian Island, Antarctica

On 20 and 22 January 2007, we observed macaroni penguins (Eudyptes chrysolophus) on Avian Island, Antarctica, approximately 1° south of the Antarctic Circle along the Western Antarctic Peninsula (WAP) near Adelaide Island, a new high-latitude observational record for the species within this region of the continent. Additionally, we report several extra-limital sightings of macaroni penguins over the last decade at relatively lower latitudes along the WAP near Anvers Island, including observations of breeding attempts. Although vagrancy cannot be ruled out as a possible causal factor in our observations, we hypothesize that a climate-induced shift in the species’ bio-geographic range may be in progress. In this context, our observations are similar to the well-documented range shifts and eventual establishment of breeding populations by other sub-Antarctic penguin species along the WAP, over the last three decades, in response to regional climate warming. We highlight that the few observations reported here do not provide conclusive evidence for any putative causal mechanism explaining the presence of macaroni penguins at locations outside their natural geographic range. However, our observations are important for developing a better understanding of the natural history of the species along the WAP.     

Detection, differentiation, and abundance estimation of penguin species by high-resolution satellite imagery

Due to its high spatial resolution, broad spatial coverage, and cost-effectiveness, commercial satellite imagery is rapidly becoming a key component of biological monitoring in the Antarctic. While considerable success in surveying emperor penguins (Aptenodytes forsteri) has been facilitated by their large size and the visual simplicity of their habitat, there has been considerably less progress in mapping colonies on the Antarctic Peninsula and associated sub-Antarctic islands where smaller penguin species breed on topographically complex terrain composed of mixed substrates. Here, we demonstrate that Adélie penguin (Pygoscelis adeliae), chinstrap penguin (P. antarcticus), gentoo penguin (P. papua), and macaroni penguin (Eudyptes chrysolophus) colonies can be detected by high-resolution (2-m multispectral, 40–50-cm panchromatic) satellite imagery and that under ideal conditions, such imagery is capable of distinguishing among groups of species where they breed contiguously. To demonstrate the potential for satellite imagery to estimate penguin population abundance, we use satellite imagery of Paulet Island (63°35′S, 55°47′W) to estimate a site-wide population of 115,673 (99,222–127,203) breeding pairs of Adélie penguins.     

Population trends and reproductive success at a frequently visited penguin colony on the western Antarctic Peninsula

Petermann Island (65°10′S, 64°10′W), one of the Antarctic Peninsula’s most frequently visited locations, is at the epicenter of a rapid shift in which an Adélie penguin dominated fauna is becoming gentoo penguin dominated. Over the course of five seasons, the breeding productivity of Adélie and gentoo penguins breeding at Petermann Island were monitored to identify drivers of this rapid community change. The impact of tourist visitation on breeding success was also investigated. Consistent with larger trends in this region, the Adélie penguin population decreased by 29% and the gentoo penguin population increased by 27% between the 2003/2004 and 2007/2008 seasons. Reproductive success among Adélie penguins ranged from 1.09 to 1.32 crèched chicks/nest, which was higher than or comparable to other sites and is an unlikely explanation for the precipitous decline of Adélie penguins at Petermann Island. Whereas gentoo penguin reproductive success was lowest in colonies frequently visited by tourists, Adélie penguin colonies frequently visited by tourists had higher reproductive success than those visited only occasionally. These results are placed in the context of other studies on reproductive success and the impact of tourist visitation on breeding colonies of Adélie and gentoo penguins.     

A new automated logging gateway to study the demographics of macaroni penguins (Eudyptes chrysolophus) at Bird Island, South Georgia: testing the reliability of the system using radio telemetry

The use of automated systems to record the identity of individual penguins and their movements in and out of a colony can provide an effective means of studying penguin biology remotely. A new gateway installed at the macaroni penguin colony at Fairy Point (513 breeding pairs in 2003) on Bird Island, South Georgia in February 2003 and the implantation of passive integrated transponders for identifying individuals is described. The reliability of the system in recording penguin arrival and departure during the end of the 2002/2003 breeding season and over the complete 2003/2004 breeding season was tested using an independent method of radio telemetry. Results from two seasons of trials indicated that there was only a 3.7% probability of the gateway missing a penguin in 2002/2003 (185 total logged crossings) and 3.9% in 2003/2004 (1,309 total logged crossings); this compared with probabilities of 16.2 and 7.9% using radio telemetry, both differences being highly significant. This automatic logging gateway is therefore shown to be a more reliable means of recording the transit of penguins between the colony and sea and, over the longer term, elucidating colony attendance and survival rates of this species at South Georgia.     

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.     

Chick growth and survival in gentoo penguins (Pygoscelis papua): effect of hatching asynchrony and variation in food supply

Summary In the gentoo penguin, Pygoscelis papua, we examined the effects of intra-clutch egg size differences and hatching asynchrony on differential chick growth and survival (including post-fledging survival), in five years for which indices of food supply were available. An initial size hierarchy within-broods at hatching was due to hatching asynchrony not intra-clutch egg size differences. In 1988 only (a poor food year), the weight advantage gained by the first-hatched (A) chick persisted to the end of brooding (30 days), with more second-hatched (B) chicks dying. There was no difference between A- and B-chick weights at fledging (60 days) or in overall chick survival between synchronous and asynchronous broods in any year. Postfledging survival (measured in one year) was not related to fledging weight or hatching order. These results provide only partial support for the hypothesis that gentoo penguins operate a brood reduction strategy to optimise chick survival in years of low food availability. We suggest that hatching asynchrony in gentoo penguins may result from selection to keep the first egg warm as soon as it is laid, due to extreme low ambient temperatures.     

Effects of long-term implanted data loggers on macaroni penguins Eudyptes chrysolophus

We tested the hypothesis that implanted data loggers have no effect on the survival, breeding success and behaviour of macaroni penguins Eudyptes chrysolophus . Seventy penguins were implanted with heart rate data loggers (DLs) for periods of up to 15 months. When compared to control groups, implanted penguins showed no significant difference in over-wintering survival rates, arrival date and mass at the beginning of the breeding season. Later in the breeding season, implanted penguins showed no significant difference in the duration of their incubation foraging trip, breeding success, fledging mass of their chicks, date of arrival to moult and mass at the beginning of the moult fast. We conclude that implanted devices had no effects on the behaviour, breeding success and survival of this species. We contrast these results to those from studies using externally attached devices, which commonly affect the behaviour of penguins. We suggest that implanted devices should be considered as an alternative to externally attached devices in order to obtain the most accurate representation of the free-ranging behaviour, ecology and physiology of penguins.     

The food and feeding ecology of the giant petrels Macronectes halli and M. giganteus at South Georgia

Giant petrels are the chief scavenging seabirds in the Southern Ocean. Quantitatively analysed regurgitations from chicks of both Macronectes halli and M. giganteus at Bird Island, South Georgia throughout the chick rearing period consisted predominantly of adult Macaroni penguins Eudyptes chrysolophus. Significant quantities of burrowing petrels and krill were taken but the amount varied in different years. Only male M. halli fed regularly at fur seal carcases. Although 10 species were found in regurgitations, squid were unimportant in the diet. Fish are possibly more important during the winter.
Intersexual differences in diet were of greater significance than interspecific ones with males taking more carrion and females more crustaceans. Chicks were fed during both day and night and in both species males received significantly more food than females during the fledging period. M. giganteus chicks received more than M. halli at all ages.
Despite their extensive reliance on carrion both species take a variety of prey and this may be especially important during the winter when penguin and seal carrion is scarce.     

Isolation and characterization of macaroni penguin (Eudyptes chrysolophus) microsatellite loci and their utility in other penguin species (Spheniscidae, AVES)

We report the characterization of 25 microsatellite loci isolated from the macaroni penguin (Eudyptes chrysolophus). Thirteen loci were arranged into four multiplex sets for future genetic studies of macaroni penguin populations. All 25 loci were tested separately in each of four other penguin species [Adélie penguin (Pygoscelis adeliae), chinstrap penguin (Pygoscelis antarctica), gentoo penguin (Pygoscelis papua) and king penguin (Aptenodytes patagonicus)]. Between eight and 12 loci were polymorphic per species. These loci are expected to be useful for studies of population genetic structure in a range of penguin species.     

Diving pattern and performance in the macaroni penguin Eudptes chrysolophus

The pattern and characteristics of diving in two female macaroni penguins Eudyptes chrysolophus was studied, during the brooding period, using continuous-recording time-depth recorders, for a total of I8 days (15 consecutive days) during which the depth, duration and timing of 4876 dives were recorded. Diving in the first 11 days was exclusively diurnal, averaging 244 dives on trips lasting 12 hours. Near the end of the brooding period trips were longer and included diving at night. About half of all trips (except those involving continuous night-time diving) was spent in diving and dive rate averaged 14–25 dives per hour (42 per hour at night). The duration of day time dives varied between trips, and averaged 1.4–1.7 min, with a subsequent surface interval of 0.5–0.9 min. Dive duration was significantly directly related to depth, the latter accounting for 53% of the variation. The average depths of daytime dives were 20–35 m (maximum depth 11 5 m). Dives at night were shorter (average duration 0.9 min) and much shallower (maximum 11 m); depth accounted for only 6% of the variation in duration. Estimates of potential prey capture rates (3–5 krill per dive; one krill every 17–20 s) are made. Daily weight changes in chicks were directly related to number of dives, but not to foraging trip duration nor time spent diving. Of the other species at the same site which live by diving to catch krill, gentoo penguins forage exclusively diurnally, making longer. deeper dives; Antarctic fur seals, which dive to similar depths as macaroni penguins, do so mainly at night.     

Population trends, breeding success and diet composition of gentoo Pygoscelis papua, magellanic Spheniscus magellanicus and rockhopper Eudyptes chrysocome penguins in the Falkland Islands. A review

Data on population size, breeding success and diet composition of gentoo (Pygoscelis papua), magellanic (Spheniscus magellanicus) and rockhopper (Eudyptes chrysocome) penguins, collected as part of the Falkland Island Seabird Monitoring Programme from 1986/1987 to 1998/1999, were analysed with regard to spatial and temporal variation, as well as potential interaction with local commercial fisheries. No significant population trends were detectable, mainly because of the short time-series and large spatial and inter-annual variation in the number of breeding pairs in the colonies monitored. However, the breeding success of all three penguin species has improved slightly over the last few years, indicating a potential for increasing populations in the near future. During the breeding season, all three penguin species preyed opportunistically on a mixture of fish, squid and crustaceans. Diet composition too showed a high degree of spatial and temporal variation. However, in all three penguin species studied, squid gradually disappeared from the diet over successive years, to be replaced by fish. Coincidentally, the commercial catches of the squid species Loligo gahi in Falkland Islands waters decreased and the by-catch of nototheniid fish increased. All three penguin species compete directly with the commercial fishing fleet for L. gahi; however, there may also be competition for Patagonian toothfish (Dissostichus eleginoides), hake (Merluccius sp.) and southern blue whiting (Micromesistius australis), because juveniles of these species were found regularly in penguin diets.     

Isolation and characterization of Campylobacter jejuni subsp. jejuni from macaroni penguins (Eudyptes chrysolophus) in the subantarctic region

On Bird Island, South Georgia, albatrosses (n = 140), penguins (n = 100), and fur seals (n = 206) were sampled for Campylobacter jejuni. C. jejuni subsp. jejuni was recovered from three macaroni penguins (Eudyptes chrysolophus). These isolates, the first reported for the subantarctic region, showed low genetic diversity and high similarity to Northern Hemisphere C. jejuni isolates, possibly suggesting recent introduction to the area.     

Interannual variation in the breeding biology of the Antarctic prion Pachyptila desolata at Bird Island, South Georgia

Interannual variation in aspects of the breeding biology of Antarctic prions was studied for three summers (1989–1992) at Bird island, South Georgia. Egg size, mass and incubation period remained constant. Laying, hatching and fledging were significantly delayed and less synchronous in 1991/92 (range of laying dates 51 days compared to 10–15 days in the two other seasons). This was due to an unusually cold and protracted winter, with ice blocking burrows into the spring, restricting availability of nest sites. Brooding lasted longer in 1991/92 but the overall fledging period was unchanged. Skeletal growth rates did not vary amongst years; growth in mass was slower in 1989/90 but fledging mass was similar in all three years. In 1989/90 and 1991/ 92 later hatched chicks grew (in mass) faster. The survival of chicks from hatching to fledging did not vary amongst years or with hatching date. Feeding frequency was similar between years, once allowance had been made for starlit nights. Thus late and asynchronous breeding in 1991/92 did not result in reduced breeding success either through predation or starvation.
Crustaceans formed 98–99% of the mass of the identifiable portion of regurgitated food samples. Significant annual variation was found within these crustaceans with the presence of krill (least in 1990/91) being inversely related to that of amphipods and copepods. There was no relationship between diet composition and chick growth or survival. Other seabird species, lacking the morphological specialization for feeding on copepods and amphipods, had very low breeding success in 1990/91, when krill was scarce.     

Aspects of the breeding biology of the southern rockhopper penguin <Emphasis Type="Italic">Eudyptes c. chrysocome</Emphasis> and new consideration on the intrinsic capacity of the A-egg

The rockhopper penguins Eudyptes chrysocome have recently been split into the northern E. moseleyi and the southern E. chrysocome rockhopper penguin. It is therefore crucial to have a comprehensive understanding of the biology of each species in order to develop appropriate conservation measures. We investigated the breeding biology of the southern rockhopper on New Island, in the western part of the Falklands Islands, by following the breeding attempt of 160 pairs during the 2006/2007 season and examining the effect of lay time and colony habitat on breeding success. Specifically, we compared survival and growth parameters between A- and B-eggs and chicks from non-manipulated and artificially manipulated nests to investigate why southern rockhopper penguins in the Falkland Islands are more able to fledge an A-egg (first laid) than conspecifics elsewhere. Breeding was highly synchronous, with no significant difference in the breeding success between early and late breeders or between pairs breeding in different habitats. We demonstrate for the first time that the A-egg produced by the southern rockhopper penguin has, when alone, the same theoretical intrinsic potential to lead to a fledged chick as the B-egg. In contrast, the hatching success and survival of the B-chick was similar when alone or in a two-egg clutch.     

Breeding and moulting fasts in macaroni penguins: Do birds exhaust their fat reserves?

• 1.1. Plasma concentrations of urea, uric acid and total lipid were compared in pre- and late-fast breeding and moulting macaroni penguins (Eudyptes chrysolophus) to test the hypothesis that birds exhaust their lipid reserves and initiate marked protein utilisation towards the end of natural fasts.
• 2.2. Male and female macaroni penguins fasted for a minimum of 29–32 days and 20 days during the breeding and moult fasts, and the difference in body weight over the sample period (reflecting body weight loss) was 31–34% and 41–47%, respectively.
• 3.3. There was no significant increase in plasma urea or uric acid at the end of either fast, nor any decrease in plasma lipid concentrations compared to pre-fast birds.
• 4.4. These results suggest that macaroni penguins continue to rely mainly on lipid reserves during the later stages of natural fasts. This is consistent with post-fast body composition data for other small penguin species.

     

First documentation of leopard seal predation of South Georgia pintail duck

Leopard seals are regular winter visitors to Bird Island, South Georgia, where they mostly prey on fur seals and penguins, and to a lesser extent on Antarctic krill and fish. Leopard seals can exploit many different species, but there are no records of predation on flying shorebirds in the wild. On 4 October 2008, an individually identified juvenile leopard seal female was observed killing and eating a South Georgia Pintail duck. It also preyed on Antarctic fur seals and gentoo and macaroni penguins during its 2-month temporary residency around the island. The varied diet of this seal exemplifies the generalist prey utilization typical of its species. Long-term diet studies at Bird Island and the published record suggest that predation on ducks is a rather exceptional finding; individual ducks are more likely to escape leopard seal attacks than penguins and provide a far less substantial ration. This note documents the first observation of this species of duck in the diet of leopard seals.     

Winter distribution and behaviour of gentoo penguins<Emphasis Type="Italic"> Pygoscelis papua</Emphasis> at South Georgia

Knowledge of the spatial and temporal dynamics of foraging penguins is important to our understanding of the Southern Ocean marine ecosystem. We use satellite tracking to provide the first data on the distribution and behaviour of gentoo penguins (Pygoscelis papua) during the winter at South Georgia. Five penguins tracked from Bird Island remained close inshore, and although they did not return to the initial tagging site, they did appear to return to land each evening. They made diurnal trips to sea of similar distance from land as those during the breeding season, even though the constraints of chick rearing were absent. Despite potential greater flexibility in their responses to variations in prey availability in winter, the penguins still returned to land each night. This may reflect benefits from conserving energy by resting on land, possibly facilitating information exchange and avoiding predation. The distribution and behaviour of gentoo penguins during the winter enables efficient exploitation of a dynamic, patchy prey resource and may ultimately determine the timing of return to the colony, and onset of breeding in the following season.