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.

     

Exogenous corticosterone and nest abandonment: A study in a long-lived bird, the Adélie penguin

Breeding individuals enter an emergency life-history stage when their body reserves reach a minimum threshold. Consequently, they redirect current activity toward survival, leading to egg abandonment in birds. Corticosterone (CORT) is known to promote this stage. How and to what extent CORT triggers egg abandonment when breeding is associated with prolonged fasting, however, requires further investigation.We manipulated free-living male Adélie penguins with CORT-pellets before their laying period. We then examined their behavioral response with respect to nest abandonment in parallel with their prolactin levels (regulating parental care), and the subsequent effects of treatment on breeding success in relieved birds.Exogenous CORT triggered nest abandonment in 60% of the treated penguins ~ 14 days after treatment and induced a concomitant decline in prolactin levels. Interestingly, prolactin levels in treated penguins that did not abandon their nest were higher at the point of implantation and also after being relieved by females, when compared with abandoning penguins. Among successful birds, the treatment did not affect the number of chicks, nor the brood mass.Our results show the involvement of CORT in the decision-making process regarding egg abandonment in Adélie penguins when incubation is associated with a natural long fast. However, we suggest that CORT alone is not sufficient to trigger nest abandonment but that 1) prolactin levels need to reach a low threshold value, and 2) a rise in proteolysis (i.e. utilization of protein as main energy substrate) seems also to be required.     

Satellite tracking of Adélie penguins

Summary Female Adélie penguins (Pygoscelis adeliae) that take too long on their first post-laying foraging trip are a major cause of breeding failure, but in the ice-filled waters of Antarctica, determining where they go and why they are away so long has proved difficult. Here we describe the first successful attempt to track penguins at sea using satellite telemetry. Four females foraged in different locations, dispelling the notion of a common feeding ground. They moved up to 272 km from the rookery and covered from 551 to 1,121 km on their trips, swimming at minimum average speeds around 1.2 m/s. The birds were most likely to be in the water between 0630 and 1430 when light intensity, important for a visual predator, was greatest. Carrying the transmitters reduced rates of fat deposition (weight gain), increasing the duration of foraging trips of females, and suggested that they may forage until their fat depots reach a minimum threshold level. This has two implications: (i) durations of these postlaying foraging trips could potentially be used as an indicator of krill abundance (Euphausia sp), the almost exclusive food of Adélie penguins during this period, and (ii) any reduction in krill stocks caused by harvesting could increase foraging trip durations with a concomitant increase mi breeding failures.     

Human-induced behaviour in Adélie penguins Pygoscelis adeliae

Summary Adélie penguins Pygoscelis adeliae appear to be little perturbed by man. We examined the incidence of nest desertion and duration of foraging trip in Adélie penguins when manipulated and fitted with devices of differing sizes. Birds with ca. 1 cm clipped from their tail feathers stayed at sea 50% longer than unmarked controls. The length of foraging trip and incidence of nest desertion increased with increasing device volume. Penguins fitted with devices did not reduce foraging trip length to that of unpackaged birds for at least 19 days. The susceptibility of Adélie penguins to disturbance should be carefully considered when activity patterns are being studied.     

Field metabolic rates of instrumented Adélie penguins using double-labelled water

Summary Adélie penguins (Pygoscelis adeliae) carrying dummy instruments were used to determine field metabolic rates using double-labelled water. All penguins injected with double-labelled water showed a marked loss of body mass (-4.5%) during the period of the experiments (20–131 h), irrespective of the time of the breeding season. Total body water averaged 57.3% and water flux estimates of field metabolic rates correlated with double-labelled water estimates of field metabolic rate (r ²=0.68), indicating that Adélie penguins do not ingest significant amounts of sea water. Brooding Adélie penguins had a mean field metabolic rate of 10.1 W·kg^-1 and at sea a field metabolic rate of 13.3 W·kg^-1, both of which compare well with previously published estimates based on time/activity budgets and respirometry. Mean field metabolic rate in penguins with crèching chicks was 14.1 W·kg^-1, and the birds spent 65 h absent from the nest as opposed to previous estimates of 7.1 W·kg^-1 and 21 h. The effects of weather, disturbance and manipulation on the behaviour and field metabolic rate of penguins late in the breeding season are discussed. Adélie penguins (crèching chicks) equipped with externally attached instruments spent more time absent from the nest than noninstrumented controls (76 vs 54 h), but had a lower field metabolic rate.Abbreviations ANOVA analysis of variance - DLW double-labelled water - FMR field metabolic rate - MR metabolic rate - RMR resting metabolic rate - TBW total body water - VSMOW Vienna standard mean ocean water - WF water flux     

Delayed laying and prolonged fasting in Adélie Penguins Pygoscelis adeliae

Observations of nesting Adélie Penguins (Pygoscelis adeliae) were made at Ardley Island during spring 1990 when snow cover was unusually thick at some subcolony sites. Adélie Penguins at these sites had to delay egg laying until the snow melted. Maximum length of fasting periods comprising pre-breeding and incubation was 50 days. Long fasting seemed to have no detrimental effect on breeding. Furthermore, there was no relationship between penguin arrival mass and duration of fast. Even birds with small mass had sufficient reserves to undergo long fasting periods.In spring 1990, when we started with a monitoring study for CEMP (CCAMLR 1990) at Ardley Island, there were still high quantities of snow at the subcolony sites. Adélie Penguins at Ardley Island inhabit both small rocky outcrops and flat, stony hillocks (storm bars). The latter had a distinctly thicker snow cover at this time so that the pebbles necessary for nest building were unattainable. Consequently, we observed the behaviour of the penguins in this situation, recorded the laying dates and lengths of fasting periods.     

Euphausia superba dominates in the diet of Adélie penguins feeding under fast sea-ice in the shelf areas of Enderby Land in summer

Adélie penguins Pygoscelis adeliae in Enderby Land, Antarctica feed mainly on Euphausia superba during the chick rearing season in shelf areas where fast sea-ice remains: indicating that E. superba is abundant under the fast sea-ice in these areas. The shelf areas in Enderby Land, therefore, are unique since the previous studies of Adélie penguin diet in Ross Sea, Adélie Land and Prydz Bay show that E. crystallorophias is the most abundant krill species in shelf areas in general.     

People in Antarctica — how much do Adélie Penguins Pygoscelis adeliae care?

Summary In the course of physiological field studies, we opportunistically examined the effects of humans and aircraft on breeding Adélie Penguins Pygoscelis adeliae. Proximity to both aircraft and humans caused substantial increases in penguin heart rate even when no external stress was manifest. A solitary human at 20 m distance from commuting penguins on a well-used pathway caused the birds to deviate by 70 m. Birds at nests exposed to a single human fled much more readily when the brood consisted of large chicks (critical distance 6.1 m) rather than small chicks (critical distance 1.3 m) or eggs (critical distance 0.3 m). Aircraft caused birds to panic at distances greater than 1,000 m and 3 days exposure to a helicopter inhibited birds that had been foraging from returning to their nests, caused bird numbers in the colonies to decrease by 15% and produced an active nest mortality of 8%. Based on this data, we make recommendations to minimize stress on Adélie Penguin colonies exposed to man.     

Pygoscelid penguins in a swim canal

Summary In Antarctica, we investigated the energy consumption of Adélie (Pygoscelis adeliae), Gentoo (P. papua) and Chinstrap (P. antarctica) penguins while resting in the water (8.4 W-kg^–1) and swimming underwater at various speeds, using a 21m long canal filled with sea-water at 4°C in conjunction with respirometry. The birds swam at will and consumed 15.7, 16.1 and 10 W·kg^–1 at the speed where cost of transport was minimal (2.1, 2.3 and 2.5 m·s^–1 in Adélie, Gentoo and Chinstrap penguins, respectively). Thermal conductance in pygoscelid penguins was 3.3 W·°C^–1. m^–2 and energy expenditure (P_i, W·kg^–1) while resting in the water is given by P_j = -0.3 t_a+9.6, where t_a is water temperature in °C. During the breeding season, pygoscelid penguins spend 25–40% of their daily energy expenditure while foraging at sea. The importance of accurate estimates of at-sea activity and energy consumption is discussed.     

Diet and reproductive success of Adélie and chinstrap penguins: linking response of predators to prey population dynamics

The diet and reproductive performance of two sympatric penguin species were studied at Signy Island, South Orkney Islands between 1997 and 2001. Each year, Adélie (Pygoscelis adeliae) and chinstrap (P. antarctica) penguins fed almost exclusively (>99% by mass) on Antarctic krill; however, there was considerable inter-annual variation in reproductive output. In 1998, chinstrap penguins were adversely affected by extensive sea-ice in the vicinity of the colony, whereas Adélie penguins were unaffected by this. However, in 2000, both species suffered reduced reproductive output. Detailed analysis of the population-size structure of krill in the diet indicated a lack of recruitment of small krill into the population since 1996. A simple model of krill growth and mortality indicated that the biomass represented by the last recruiting cohort would decline dramatically between 1999 and 2000. Thus, despite the lack of a change in the proportion of krill in the diet, the population demographics of the krill population suggested that the abundance of krill may have fallen below the level required to support normal breeding success of penguins sometime before or during the 2000 breeding season. The role of marine predators as indicator species is greatly enhanced when studies provide data reflecting not only the consequences of changes in the ecosystem but also those data that elucidate the causes of such changes.     

Dynamics of antarctic penguin populations in relation to inter-annual variability in sea ice distribution

To investigate the role of sea ice cover on penguin populations we used principal component analysis to compare population variables of Adélie (Pygoscelis adeliae) and chinstrap (Pygoscelis antarctica) penguins breeding on Signy Island, South Orkney Islands with local (from direct observations) and regional (from remote sensing data) sea ice variables. Throughout the study period, the Adélie penguin population size remained stable, whereas that of chinstrap penguins decreased slightly. For neither species were there significant relationships between population size and breeding success, except for an apparent inverse density-dependent relationship between the number of Adélie breeding pairs and the number of eggs hatching. For both species, no general relationship was found between either population size or breeding success and the local sea ice conditions. However, the regional sea ice extent at a particular time prior to the start of the breeding season was related to the number of birds that arrived to breed. For both species, this period occurred before the sea ice reached its maximum extent and was slightly earlier for Adélie than for chinstrap penguins. These results suggest that sea ice conditions outside the breeding season may play an important role in penguin population processes.     

Diet of Adélie penguins Pygoscelis adeliae during the post-hatching period at Esperanza Bay,Antarctica, 1987/88

The diet of the Adélie penguin Pygoscelis adeliae was studied at Esperanza Bay, Antarctic Peninsula, during the post-hatching period by quantitative analysis of adult stomach contents. Euphausiids constituted on average 96% by mass, while fish contributed 4% by mass. Amphipods were present in small amounts. Antarctic krill Euphausia superba was the predominant component throughout the sampling period. In contrast, Euphausia crystallorophias occurred rarely. Differences in the size of krill taken by Adélie penguins appear to reflect either local changes in the availability of certain age classes at various times in the breed ing season, or differences in foraging areas, or are due to year-to-year differences in prey availability and abundance, possibly caused by variations in seasonal ice cover. Pleuragramma antarcticum constituted the bulk of the fish portion, particularly during the guard period.     

The diets of five summer breeding seabirds in Adélie Land,Antarctica

Summary The diets of five breeding seabird species were investigated on Adélie Land in January–February 1982. Stomach contents of Adélie penguins, Pygoscelis adeliae, were sampled by a water off-loading method and of Procellariiformes by spontaneous regurgitation. Diet compositions by mass were: Adélie penguin (79% euphausiid, 18% fish, 3% squid); Cape pigeon, Daption capense, (64% euphausiid, 29% fish, 7% carrion); Antarctic fulmar, Fulmarus glacialoides, (64% euphausiid, 20% carrion, 16% fish); snow petrel, Pagodroma nivea, (95% fish, 2% euphausiid, 1% carrion) and Wilson's stormpetrel, Oceanites oceanicus, (39% fish, 37% euphausiid, 13% carrion, 12% various crustaceans). The present Adélie penguin diet is consistent with those reported in other studies, given our knowledge of geographical variation in food availability. Differences in the diets of fulmarine petrels appear to relate to differences in foraging areas. The snow petrel is a fish-eating bird associated with pack-ice. Cape pigeon and Antarctic fulmar are mainly krill-eaters and we infer segregation along a neritic/oceanic gradient because of the importance of the neritic Euphausia crystallorophias in the former and the oceanic E. superba in the latter.     

Adélie penguin parental activities and reproduction: effects of device size and timing of its attachment during chick rearing period

Summary Effects of device attachment on parental activities and body mass change in instrumented birds and their mates, and on chick growth and survival, were studied in Adélie Penguins Pygoscelis adeliae in Lützow-Holm Bay, Antarclica. Penguins on which small devices were fitted with rubber band harnesses exhibited increased foraging trip duration, and decreased body mass, food delivery rate, chick growth and chick survival. Their mates did not increase food delivery rate. Those on which small or large devices were fitted with epoxy glue did not change foraging trip duration, body mass, or chick survival. However, large devices decreased chick growth. These effects were more obvious; among penguins fitted with devices later in the chick rearing period, and suggest that: 1) parents fitted with devices give a priority to maintenance of their own energy reserve over guarding and food delivery for chicks; and, 2) parents' decreasing energy reserves later in the breeding season might intensify the effects of devices.     

Seasonal occurrence and dominance of Centropages congeners in the Middle Atlantic Bight,USA

The distribution and abundance of 15 taxa of birds seen from a vessel in the region of Prydz Bay, Antarctica between November and December 1982 are presented. Antarctic petrels were by far the most frequent in the survey area while Adélie and emperor penguins made up 77% of the observed avian biomass. The distribution and abundance of birds was found to be related to ice conditions, air temperature and wind speed but not to water temperature or air pressure. The extent of species associations at sea are shown and the possibilities of diurnal fluctuations in bird numbers at sea are examined.     

Moulting fast and time constraint for reproduction in the king penguin

King penguins (Aptenodytes patagonicus) replace their complete plumage during a 3- to 4-week moulting fast on shore. After moulting, birds forage at sea for 2-3 weeks to store energy reserves for reproduction. Using an automatic identification and weighing system coupled with visual observations, we investigated the trade-off between the moulting fast and the following breeding attempt, in terms of body condition and in relation to time constraints, in free-living king penguins. King penguins reached their lowest body mass of the yearly cycle at the end of the moulting fast; this was lower than that at the end of the incubation fasts and not different from the body mass at egg desertion. Later in the season, the duration of the moulting fast became shorter and old feather loss occurred earlier after arrival ashore. Postmoulting foraging trips were shorter, but at the expense of body condition at the beginning of courtship. These results are discussed in relation to the synchronisation of the breeding cycle with food availability and mate choice.     

Estimating the critical body mass of king penguins

King penguins (Aptenodytes patagonicus) can fast for over a month. However, they return to sea to forage before their body mass reaches a critical value (cMb), beyond which there is an increase in rate of mass loss and in protein catabolism, termed phase III of fasting. Thus when studying king penguins onshore, accurate estimation of their cMb and, in turn, the date at which that body mass would be reached, will be informative to behavioural and physiological data being collected. For penguins being studied during fasts in captivity, knowing cMb is particularly important because of the need to release the birds back into their colony while they are still in good nutritional condition. The present study investigates the validity of using measures of beak, flipper and foot length together to estimate cMb in king penguins and provides a simple and effective prediction equation for researchers. The three morphometric measurements, along with body mass just prior to going to sea after the moult fast (taken to represent cMb), were obtained for nine king penguins in a colony at the Crozet Archipelago. A multiple linear regression of the three morphometric measurements against cMb provided an R ² of 71.2%. Mean absolute percentage error of the estimate of cMb over the nine birds was 8.82 ± 1.20%. The described technique could probably be employed for estimating cMb in other long-fasting seabirds.     

Foraging rhythms in Adélie penguins (Pygoscelis adeliae) at hope bay,Antarctica; determination and control

Summary We studied diel periodicity in activity of Adélie penguins (Pygoscelis adeliae) during the austral summer solstice and one month later by counting, hourly, numbers of birds leaving colonies to forage, numbers arriving back after foraging, numbers in a colony and numbers resting outside the colonies. During the solstice large numbers of birds were arriving at and departing from the colony at all times of the day although there was a tendency for more birds to be at sea when light intensity was highest at mid-day. Generally, birds not brooding chicks did not rest on land. A month later, when visibility was poor at mid-night, the percentage of birds at sea was highly positively correlated with light intensity. Birds returning from foraging in the evening fed chicks immediately and then either rested in the colonies or on snow patches between the colonies and the sea until the following morning.     

Fluoride turnover in adélie penguins (Pygoscelis adeliae) and other brid species

Summary Fluoride concentrations found in soft tissues of free ranging birds are below 10 mg/kg d.w. In ducks (Anas platyrhynchos) 99.5% of all fluoride is bound in the skeleton. Krill-eating adélie penguins (Pygoscelis adeliae) reached equilibrium concentrations in the order of 10000 mg F/kg d.w. in femur. Fluoride uptake with the diet is buffered by the skeleton where it has a half-life of 3–4 weeks. Fluoride from fresh krill does not reach the organs of adélie penguins to the same extent as NaF. Most fluoride remains bound to the krill cuticle and is not absorbed by the penguin gut during digestion. The availability of krill fluoride was in the range of 21%–30% for muscle and 48%–68% for femur of adélie penguins as compared to NaF (100%). The role of the salt glands in fluoride excretion is neglegible. The uptake of approx. 240 mg F daily with the krill diet is balanced by excretion via the cloaca.This work was supported by a grant from the DFG Nr. MZ-AD 24/9 and by a stipend from the Studienstiftung des deutschen Volkes     

Energetic costs of raising Pygoscelid penguin chicks

Energy requirements of resting Adélie (Pygoscelis adeliae), Gentoo (P. papua) and Chinstrap (P. antarcticd) penguin chicks were determined with respect to body mass via respirometry in Antarctica. Resting metabolic rates of all Pygoscelid penguin chicks were similar (ANOVA p=0.91) and best described by E=0.0096 M^0.98 (n=24, r²=0.97), where E is power (W) and M is mass (g). Using the results obtained here and data published in the literature, I determined a) the amount of food needed from hatching to fledging as 29.8, 31.7 and 56.4 kg per chick for Adélie, Chinstrap and Gentoo penguins, respectively and b) the average amount of food left daily to the parent after feeding the brood throughout the breeding period. Parents keep only a minimum of food for themselves just prior to the time when chicks begin forming crèches. Thereafter, nest relief intervals are increased, and the amount of food parents can keep for themselves rises. The results of both models are discussed with respect to available data on Pygoscelid penguin food requirements.