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.     

Stable isotopes reveal Holocene changes in the diet of Adélie penguins in Northern Victoria Land (Ross Sea, Antarctica)

Adélie penguin (Pygoscelis adeliae) modern and fossil eggshells and guano samples collected from ornithogenic soils in Terra Nova Bay (Victoria Land, Ross Sea) were processed for carbon and nitrogen isotopic ratios with the aim of detecting past penguin dietary changes. A detailed and greatly expanded Adélie penguin dietary record dated back to 7,200 years BP has been reconstructed for the investigated area. Our data indicate a significant dietary shift between fish and krill, with a gradual decrease from past to present time in the proportion of fish compared to krill in Adélie penguin diet. From 7,200 to 2,000 years BP, δ¹³C and δ¹⁵N values indicate fish as the most eaten prey. The dietary contribution of lower-trophic prey in penguin diet started becoming evident not earlier than 2,000 years BP, when the δ¹³C values reveal a change in the penguin feeding behavior. Modern eggshell and guano samples reveal a major dietary contribution of krill but not a krill-dominated diet, since δ¹³C values remain much too high if krill prevail in the diet. According to the Holocene environmental background attested for Victoria Land, Adélie penguin dietary shifts between fish and krill seem to reflect penguin paleoecological responses to different paleoenvironmental settings with different conditions of sea-ice extension and persistence. Furthermore, Adélie penguin diet appears to be particularly affected by environmental changes in a very specific period within the breeding season, namely the egg-laying period when penguin dietary and feeding habit shifts are clearly documented by the δ¹³C of eggshell carbonate.     

Annual variation in reproductive parameters of Adélie penguins at Edmonson Point,Victoria Land,Antarctica

Annual egg and chick production and breeding success at the Adélie penguin (Pygoscelis adeliae) colony Edmonson Point (74°21′S–165°10′E), Victoria Land, is presented for eight breeding seasons between 1995 and 2005. During this period the colony consisted of 10–13 subcolonies and averaged 2098 ± 278 breeding pairs. A sample of over 100 nests (114–150), belonging to two subcolonies, was monitored each year. Some breeding parameters remained constant while others showed substantial annual variation. Laying date showed little variation, and laying was highly synchronous: 82.5% of clutches were initiated in a 10-day period, 9–18 November. In contrast, clutch size (1.77–1.97) and incubation period (34.4 ± 2.5) varied significantly. Variation among years was also recorded in hatching success (from 58 to 86%) and breeding success. This last parameter, measured as number of chicks reared to crèche per nest with eggs, varied between 0.34 and 0.97.     

Using logistic regression models to predict breeding success in male Adélie penguins (Pygoscelis adeliae)

Measures of breeding success are traditionally derived using the proportion of total nests that successfully reach strategic stages across a breeding season, such as pair formation, egg laying or fledging chicks. The use of logistic regression has recently become a popular tool in avian literature for identifying influential factors that predict nest and/or individual breeding success. In this study, we use logistic regression models to assess the importance of a range of factors affecting male Adélie penguin (Pygoscelis adeliae) breeding success during the 2002–2003 austral summer, when the presence of icebergs and extensive sea-ice meant overall breeding success of Adélie penguins was low (16/51 focal males had chicks reach fledging point). Logistic regression models for the early breeding season showed that good/average nest quality and central/middle nest location within the sub-colony were the best predictors of successful pair formation. Later, during incubation, the most successful males were those that not only returned earlier but were also heavier upon arrival and built nests of at least average quality. During the final stage when chicks had begun to fledge, the combined parameters of heavier male weight, early arrival time and good nest quality were the best predictors of breeding success. The logistic regression approach used here showed that the predictive ability of these parameters varied as the season progressed. However, most importantly, our logistic models fit the data well across all breeding stages.     

Post-breeding dispersal of Ad��lie penguins (Pygoscelis adeliae) nesting at Signy Island, South Orkney Islands

ARGOS satellite telemetry and Global Location Sensors (geolocators) were used to identify the moult locations and the winter foraging dispersal of Adélie penguins after they left their breeding colonies on Signy Island in the South Orkney Islands. Animals were tracked during the period December 2004 to October 2005. All birds displayed a similar pattern of migratory behaviour, remaining away from colonies for approximately 9 months, at distances of up to 2,235 km. Moult locations were within the pack ice. Mean daily travel speeds to the moult locations were significantly faster when moving through open water than through pack ice. Moult occurred during February/March within a narrow latitudinal range (65–71°S), at a mean distance of 126 km from the ice edge; the mean duration of individual moult was c. 18.6 days. After moult, penguins spent the subsequent winter months moving north or north-eastward within the expanding winter pack ice, at a mean distance of 216 km from the ice edge, and in areas with ice cover >80%. The penguins returned to the vicinity of their colony between September 26 and October 22, 2005. This dependence of Adélie penguins on sea ice habitat suggests that any further reductions in sea ice extent in the Weddell Sea region would potentially have important impacts on the population processes of this pagophilic species.     

Adverse effects of instrumentation in incubating Adélie penguins (Pygoscelis adeliae)

The use of data-loggers has permitted to explore the biology of free-ranging animals. However, this method has also been reported to reduce reproductive success while the reasons of this deleterious effect remain poorly documented. In this study, we aimed to identify critical periods of the breeding cycle of Adélie penguins (Pygoscelis adeliae) when the reproductive success may decrease because of instrumentation. For this purpose, we monitored 40 pairs, where one parent was instrumented before egg laying and 30 pairs without devices (controls). These pairs were followed at least during the incubation period but the majority was monitored during the entire breeding season. Reproductive success was affected in pairs where males were instrumented. This was not due to extra chick mortality during chick rearing but to a significantly lower hatching success. Moreover, the use of artificial eggs recording incubation temperatures and egg rotation indicated that in instrumented incubating males, eggs spent as much time at optimal incubation temperatures as control eggs but were rotated at a higher frequency. In Adélie penguins, males initiate incubation and it has been established that the early stage of incubation is one of the most critical periods for embryonic development. The low hatching rate observed in instrumented males was associated with a higher egg rotation rate, perhaps as a stress response to the presence of the instrument. Even though the causal effects remain unclear, instrumentation severely affected hatching success. For these reasons, we recommend equipping birds after the early incubation.     

An albinistic Adélie penguin breeding at Amundsen Bay, Antarctica

An albinistic penguin of Pygoscelis adeliae, found in the colony located in the southwestern part of the Mt. Riiser-Larsen area, Amundsen Bay, Enderby Land, was incubating a single egg. Accepted: 18 September 1999     

Annual and seasonal changes in foraging site and diving behavior in Adélie penguins

Foraging sites, diet, and diving behavior of chick-rearing Adélie penguins, Pygoscelis adeliae, in fast sea-ice areas were investigated during two consecutive seasons with contrasting sea-ice conditions. During 1995/1996, fast sea ice covered the foraging range of penguins during the whole breeding season. In contrast, during 1996/1997, sea ice covered the area in December 1996, but gradually thinned and finally broke up, so that open sea appeared along the coast during February 1997. Foraging sites were concentrated in a small area in 1995/1996 and spread over a wider area in 1996/1997 as more small open-water areas were available. In both seasons, parents traveled to more distant foraging sites as the season progressed and, consequently, the foraging-trip duration increased. In both years, Euphausia superba and Pagothenia borchgrevinki dominated the diet in the early part of the season, while later in the season penguins fed mainly on E. superba in 1995/1996 and Pagothenia borchgrevinki and E. crystallorophias in 1996/1997. In 1995/1996, penguins tended to dive deeper—albeit for a relatively shorter duration—when feeding mainly on krill compared to when feeding on fish. In 1996/1997, there was no difference in the dive depth and duration between krill- and fish-eating trips. Our results suggest that prey distribution changes annually and seasonally, probably according to sea-ice conditions, and that consequently penguins modify their foraging sites, diving patterns, and diet according to these changes.     

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.     

Satellite telemetry of the winter migration of Adélie penguins (Pygoscelis adeliae)

Adélie penguins (Pygoscelis adeliae), after breeding in Antarctica during the austral summer, undergo a winter migration before returning to the breeding grounds 8 months later. It is the major source of adult mortality, with about a quarter of them not returning. Here we describe the first attempt to track the winter migration of Adélie penguins using satellite telemetry. Transmitters were attached to two penguins on 16 February 1991 after their post-breeding moult at Cape Bird, Ross Island, Antarctica. Transmissions were received from one penguin (bird #1) for 4.4 months, during which time it travelled 2792.6 km from the rookery (nearly 1500 km straight-line distance). Transmissions were received from the other penguin (bird #2) for 2.5 months during which time it followed a path remarkably similar to that of bird #1. The penguins travelled northwards up the coast of Victoria Land, keeping within 100 km of the coast, rounding Cape Adare soon after 29 March and were midway between the Balleny Islands and the Antarctic coast on 3 May. Thereafter, the record from bird #1 shows that it travelled further westwards until, when opposite the Mastusevich Glacier Tongue of the Mastusevich Glacier, it turned due north and moved away from the coast. By 29 June, when transmissions ended, its progression had slowed and it was northwest of the Balleny Islands near a zone where pack ice covered 75% of the surface of the sea. Two novel points that arise from this study are: (1) that Adélie penguins from Cape Bird undergo winter migrations of not less than 5000 km, and (2) that they may be travelling to common overwinter feeding grounds.     

Diving behaviour of chick-rearing Adélie Penguins at Edmonson Point, Ross Sea

The diving behaviour of chick-rearing Adélie penguins of Edmonson Point, Ross Sea, was analysed over two summer seasons (1994–1995 and 1995–1996). In 1994–1995, the study area was characterized by fast-ice persistency throughout season and by higher pack ice concentration than the following year, when fast-ice retreated earlier. Both females’ and males’ behaviour were examined, and we then compared diving characteristic between years and between guard and crèche stages of chick rearing. We found that changes in fast-ice extent influenced the transit times between colony and foraging grounds and that females conducted longer foraging trips, dived for longer periods and made more dives than males. The diving parameters were affected neither by the sex nor by the year, but differed between the breeding stages. Parents guarding chicks had longer dive and bottom phase durations than in crèche (dive duration: guard = 48 s, crèche = 42 s; bottom duration: guard = 34 s, crèche = 26 s), whilst they had shorter recovery times (e.g. post dive duration) (guard = 29 s, crèche = 32 s). Possible causes for the observed differences in diving behaviours are discussed.     

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.     

In situ heart rate and activity of incubating Adélie penguins (Pygoscelis adeliae)

Summary Heart rates and activity were monitored over 24 h in unrestrained, incubating Adélie penguins (Pygoscelis adeliae) exposed to natural conditions in the colony. Heart rate (HR in bpm) increased linearly with wind speed (w; range 0–19 m/s): HR = 85.8+1.35 w, but was unrelated (P>0.05) to temperature (-2.5°–6°C), humidity (37%–100%) cloud cover (0–8/8) and estimated solar radiation (0–12). Wind-induced heat loss was apparently compensated to a large degree by increased metabolic activity. Activity (A) measured as frequency of standing per hour, decreased linearly with temperature (t) and wind speed (w): A = 1.651–0.033w–0.090t. After correcting for meteorological influences, heart rate and bird activity showed no diurnal periodicity. When incubating, metabolism and activity of Adélie penguins appear to be mainly governed by climatic variations.     

Observations on the thermal conductance of Adélie (Pygoscelis adeliae) and Humboldt (Spheniscus humboldti) penguins

 Analyses of cooling rates in one Adélie and one Humboldt penguin yielded calculated thermal conductance values of 0.1040 and 0.1672 W(kg ^°C)^-1, respectively. We review the methods used to calculate penguin surface area, an important component in calculating conductance values, and suggest that, in comparative studies of thermal balance, the use of body mass is a better estimator of body size than surface area. Using previously published data on penguin species, we found a significant model to predict thermal conductance from body mass according to: log C= log 0.1083−0.474 log M, where C is minimal specific thermal conductance in W(kg ^°C)^-1 and M is body mass in kilograms. Received: 13 June 1995/Accepted: 11 March 1996     

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     

Adélie penguin (Pygoscelis adeliae) survival rates and their relationship to environmental indices in the South Shetland Islands,Antarctica

Seabird life history is typified by low fecundity, high adult survival rates, and relatively long lives. Such traits act as buffers, enabling persistence of populations under variable environmental conditions. Numerous studies, however, have suggested strong sensitivity of seabirds to environmental variability. In the Antarctic Peninsula region, for example, Adélie penguin (Pygoscelis adeliae) populations have declined during the last three decades, attributed largely to rapid changes in environmental conditions and food availability. We use 30 years of mark-recapture data from known-age individuals in the South Shetland Islands and capture-mark-recapture models to estimate survival rates with respect to such environmental variation. We investigated specifically whether negative trends in survival rates were evident and whether indices of global, regional, and local environmental conditions considered important for Adélie penguin survival explained the variability in survival rates. Overall, negative trends in juvenile survival were evident, but adult survival rates exhibited high interannual variability. Indices of sea ice extent had the strongest correlations with survival rates, particularly Weddell Sea ice extent during spring among adults (r = 0.62) and during winter for juveniles (r = 0.46). An analysis of deviance, however, suggested that single environmental covariates explained <30 % of the observed variation in the full mark-recapture models. Despite positive effects of sea ice extent on survival rates of Adélie penguins, limited explanatory power of several environmental conditions previously identified as important for Adélie penguin survival underscores the difficulty of predicting future population responses in this region of rapid environmental change.     

Fluoride excretion in adélie penguins (Pygoscelis adeliae) and mallard ducks (Anas platyrynchos)

• 1.1. Chronic F⁻ doses of NaF (40 and 80mg F⁻/kg per day) given to adélie penguins for 6–7 weeks led to a significant increase in F⁻ concentrations of nasal salt secretions with 1.16 and 2.22μg F⁻/g (wet wt) respectively as opposed to 0.66 μg F⁻/g in controls.
• 2.2. Single oral administration of 6 mg fluoride as NaF to mallard ducks led to increased F⁻ concentrations in the nasal salt secretions, with a mean of 0.67μg F⁻/g as opposed to 0.11 μg F⁻/g in controls.
• 3.3. In mallard ducks as well as in adélie penguins the amount of F⁻ excreted via the cloaca was 10³-10⁴ times that excreted via the nasal salt glands.

     

Changes in Adélie penguin breeding populations in Lützow-Holm Bay, Antarctica, in relation to sea-ice conditions

The Adélie penguin, Pygoscelis adeliae, an important component of the Antarctic marine ecosystem, is closely associated with sea ice. Using data collected by Japanese Antarctic Research Expeditions since the 1960s, we examined trends in breeding populations of this species around Lützow-Holm Bay. Ten colonies ranging in size from 10 to 2,500 individuals were counted along the Soya Coast. Populations fluctuated synchronously, and overall increased at most colonies, except for two: one located deep inside the bay and another where human disturbance was substantial. Populations tended to increase during, or after, periods of sparse sea ice in summer, a condition that occurred once every decade. An increase in population size also occurred 5 years after a winter of extensive sea ice and after a winter of especially reduced sea ice.     

Mega-epibenthic diversity off Terre Adélie (Antarctica) in relation to disturbance

Mega-benthic assemblages have been analyzed off Terre Adélie (East Antarctica) between 20 and 110 m depth by seabed videography. The study area is dominated by high abundances of sessile suspension feeders, however, sponges are rare at this depth. There are hints and evidence that different levels of disturbance and biological dynamics affect these assemblages. Biodiversity results are interpreted with the background of an applicability of the intermediate-disturbance hypothesis (IDH).     

Sex-Based Differences in Adélie Penguin (Pygoscelis adeliae) Chick Growth Rates and Diet

Sexually size-dimorphic species must show some difference between the sexes in growth rate and/or length of growing period. Such differences in growth parameters can cause the sexes to be impacted by environmental variability in different ways, and understanding these differences allows a better understanding of patterns in productivity between individuals and populations. We investigated differences in growth rate and diet between male and female Adélie Penguin (Pygoscelis adeliae) chicks during two breeding seasons at Cape Crozier, Ross Island, Antarctica. Adélie Penguins are a slightly dimorphic species, with adult males averaging larger than adult females in mass (~11%) as well as bill (~8%) and flipper length (~3%). We measured mass and length of flipper, bill, tibiotarsus, and foot at 5-day intervals for 45 male and 40 female individually-marked chicks. Chick sex was molecularly determined from feathers. We used linear mixed effects models to estimate daily growth rate as a function of chick sex, while controlling for hatching order, brood size, year, and potential variation in breeding quality between pairs of parents. Accounting for season and hatching order, male chicks gained mass an average of 15.6 g d^-1 faster than females. Similarly, growth in bill length was faster for males, and the calculated bill size difference at fledging was similar to that observed in adults. There was no evidence for sex-based differences in growth of other morphological features. Adélie diet at Ross Island is composed almost entirely of two species—one krill (Euphausia crystallorophias) and one fish (Pleuragramma antarctica), with fish having a higher caloric value. Using isotopic analyses of feather samples, we also determined that male chicks were fed a higher proportion of fish than female chicks. The related differences in provisioning and growth rates of male and female offspring provides a greater understanding of the ways in which ecological factors may impact the two sexes differently.