Pygoscelis

Abstract: We measured corticosterone in plasma collected from free-living Adelie Penguins (Pygoscelis adeliae) and made blood smears to count the ratio of heterophils to lymphocytes (H/L). Our objective was to categorize how these two measures of stress vary with potential stressors in the birds' environment. In penguins that were repeatedly sampled from three to eight times, repeated handling did not affect corticosterone levels or H/L, but there were significant differences among individuals. Nesting stage did not affect corticosterone level, but H/L was significantly lower during the chick stage than in the courting or incubation stages. Sex and handling times of less than 5 min had no effect on either corticosterone or H/L. In birds that had fasted up to 40 days during the courtship and early incubation stages, there was no increase in corticosterone or H/L with length of fasting, but in birds that had fasted more than 50 days, corticosterone levels increased. Birds with obvious injuries had significan...

Abstract: Measurement of the time allocation of penguins at sea has been a major goal of researchers in recent years. Until now, however, no equipment has been available that would allow measurement of the aquatic and terrestrial behaviour of an Antarctic penguin while it is commuting between the colony and the foraging grounds. A new motion detector, based on the measurement of acceleration, has been used here in addition to current methods of inferring behaviour using data loggers that monitor depth and speed. We present data on the time allocation of Adelie penguins (Pygoscelis adeliae) according to the different types of behaviours they display during their foraging trips: walking, tobogganing, standing on land, lying on land, resting at the water surface, porpoising and diving. To illustrate the potential of this new technique, we compared the behaviour of Adelie penguins during the chick-rearing period in a fast sea-ice region and an ice-free region. The proportion of time spent standing, lying on land and walking during foraging trips was greater for penguins in the sea-ice region (37.6+/-13.3% standing, 21.6+/-15.6% lying and 5.9+/-6.3% walking) than for those in the ice-free region (12.0+/-15.8 % standing, 0.38+/-0.60% lying and 0 % walking), whereas the proportion of time spent resting at the water surface and porpoising was greater for birds in the ice-free region (38.1+/-6.4% resting and 1.1+/-1.1% porpoising) than for those in the sea-ice region (3.0+/-2.3% resting and 0% porpoising; means +/- s.d., N=7 for the sea-ice region, N=4 for the ice-free region). Using this new approach, further studies combining the monitoring of marine resources in different Antarctic sites and the measurement of the energy expenditure of foraging penguins, e.g. using heart rates, will constitute a powerful tool for investigating the effects of environmental conditions on their foraging strategy. This technique will expand our ability to monitor many animals in the field.

Abstract: As important marine mesopredators and sensitive indicators of Antarctic ecosystem change, penguins have been a major focus of long-term biological research in the Antarctic. However, the vast majority of such studies have been constrained by logistics and relate mostly to the temporal dynamics of individual breeding populations from which regional trends have been inferred, often without regard for the complex spatial heterogeneity of population processes and the underlying environmental conditions. Integrating diverse census data from 70 breeding sites across 31 years in a robust, hierarchical analysis, we find that trends from intensely studied populations may poorly reflect regional dynamics and confuse interpretation of environmental drivers. Results from integrated analyses confirm that Pygoscelis adeliae (Adelie Penguins) are decreasing at almost all locations on the Antarctic Peninsula. Results also resolve previously contradictory studies and unambiguously establish that P. antarctica (Chinstrap Penguins), thought to benefit from decreasing sea ice, are instead declining regionally. In contrast, another open-water species, P. papua (Gentoo Penguin), is increasing in abundance and expanding southward. These disparate population trends accord with recent mechanistic hypotheses of biological change in the Southern Ocean and highlight limitations of the influential but oversimplified "sea ice" hypothesis. Aggregating population data at the regional scale also allows us to quantify rates of regional population change in a way not previously possible.

Abstract: -The species composition and characteristics of prey consumed by sympatrically breeding Ad&e, Chinstrap, and Gentoo penguins were determined by analysis of whole stomachs collected at Point Thomas, King George Island, South Shetland Islands, Antarctica (62”1O’ S, 58”3O’ W) during the 1977-1978 breeding season. All three penguins consumed primarily one species of euphausiid, Euphausia superba, although Gentoo Penguins ate significantly more fish, Pleurogramma antarcticum, than either Ad&lie or Chinstrap penguins. E. crystallorophias, and pelagic and benthic species of amphipods were minor components of the pygoscelid diet. The penguins differed in euphausiid size and in the ratios of male, female, and adolescent euphausiids eaten. These differences were consistent over the entire reproductive cycle. In addition, the species differed in the wet weight of fish consumed by Gentoo Penguins, and in the length of euphausiids consumed by Ad&lie Penguins. We suggest that these differences in diets are due, in part, to geographical and temporal differences in feeding areas and habitats. The breeding ranges of the pygoscelid penguins, the Ad&lie (Pygoscelis adeliae), the Chinstrap (P. antarctica), and the Gentoo (P. Papua) overlap in the area of the Antarctic Peninsula, and the birds breed sympatrically at several locations. Whether or not they compete for certain resources (e.g., food and nesting habitat) has recently been much discussed (Conroy et al. 1975a, b, White and Conroy 1975, Trivelpiece and Volkman 1979, Volkman and Trivelpiece, in press). The diets of pygoscelid penguins consist of euphausiid crustaceans, mainly Euphausia superba, shoaling fishes, and amphipods (Conroy et al. 1975a, b, White and Conroy 1975, Croxall and Furse 1980, Croxall and Prince 1980). Although White and Conroy (1975) proposed that sympatric pygoscelids consume different prey species and/or prey of different size classes, data to support their hypothesis are limited. In order to further examine the feeding ecology of this genus, during the austral summer of 1977-1978, we collected whole stomachs from Ad&lie, Chinstrap, and Gentoo penguins. We wished to quantify the type, abundance and characteristics (e.g., sex, age class, etc.) of the prey species selected by each of the pygoscelids, and to examine any seasonal variation in these measurements. METHODS This study was conducted at Point Thomas, King George Island, South Shetland Islands, Antarctica (62”1O’ S, 58”3O’ W) from 1 November 1977 to 21 Fehruary 1978. All three pygoscelid penguins breed in two rookeries (after Penney 1968) at Point Thomas. The rookeries are separated by a glacial tongue, and are about 3 km apart. An estimated 7,000 Ad&e, 290 Chinstrap, and 1,900 Gentoo pairs breed in the East rookery; 11,000 Ad&lie, 750 Chinstrap, and 700 Gentoo pairs breed in the West rookery. The Polish Academy of Sciences Antarctic Station, Henryk Arctowski, is located 1 km south of the West rookery. Emison’ s (1968) technique for pumping the stomachs of Ad&lie Penguins by orally inserting a hollow plexiglass tube was inapplicable to our study. Samples collected by stomach pumping and compared with contents of complete stomachs taken from the same bird revealed significant differences. Many organisms in whole stomach samples measured 40 to 50 mm, while those in pumped samples were 20 to 35 mm long. Larger krill apparently did not fit in the tube, or were broken during collection. In addition, because different prey species occurred in distinct layers in the stomachs, pumped samples were not always representative of the type of prey species present. The discrepancies between samples collected with stomach tubes, and those from whole stomachs necessitated the use of the latter method in this study. We first used a stomach tube, however, to ensure that only penguins with stomach contents would be killed. Complete stomach samples were collected from 48 adult Ad&lie (26 males, 22 females), 29 adult Chinstrap (14 males, 15 females), and 46 adult Gentoo (24 males, 22 females) penguins during the course of the breeding cycle. Penguins with highly vascularized brood patches were caught and killed only in the East rook-