Gentoo Penguins Pygoscelis Papua Research Articles

Diving Pattern and Performance in Nonbreeding Gentoo Penguins (Pygoscelis papua) during Winter

ABSTRACr.-We studied diving patterns and performance (dive depth, duration, frequency and organization during the foraging trip) in relation to diet in nonbreeding Gentoo Penguins (Pygoscelis papua) over 59 days (involving 5,469 dives) in winter. We estimated foraging ranges and prey capture rates, and compared foraging behavior with that of breeding (chick-rearing) birds. Foraging was highly diurnal with 98% of foraging trips completed during the same day. Foraging-trip frequency was 0.8/day, trip duration was 6-8 h, and birds spent 51-62% of the foraging trip diving. Dive depth and duration were bimodal. Shallow dives ( 30 m; 55% of total number and 81% of dive time) averaged 74-105 m and 2.7-3.5 min, respectively. Deep-dive duration exceeded the subsequent surface interval, but shallow dives were followed by surface intervals two to three times dive duration. Deep dives showed clear diel patterns, averaging 10-20 m at dawn and dusk and 70-90 m at midday. These results are consistent with the patchy vertical and horizontal distribution and diel movements of Antarctic krill, the main winter prey of Gentoo Penguins (including study birds). We suggest that shallow dives are mainly searching dives, and deep dives mainly for feeding. Foraging activity of nonbreeding Gentoo Penguins in winter is similar to that of chick-rearing birds. The only major differences are that foraging-trip frequency is 20% less and stomachcontent mass on return ashore 30% less in winter. We conclude that foraging activity in Gentoo Penguins is changed by varying the frequency and duration of foraging trips, rather than by changing the pattern and rate of diving. Received 6 December 1990, accepted 10 January 1992.

Embryonic metabolism, energy budgets and cost of production of king Aptenodytes patagonicus and gentoo Pygoscelis papua penguin eggs

1. 1. Embryonic oxygen consumption ( MO 2) of King Aptenodytes patagonicus and Gentoo Pygoscelis papua Penguins was similar to that of precocial or semi-precocial hatchlings, although behavioural traits suggest altricial hatchlings. 2. 2. In spite of the relatively longer incubation period and contrary to expectations, relative yolk contents of fresh King and Gentoo Penguin eggs were similar although energy density of King Penguin eggs was slightly higher. However, hatchling mass of King Penguins was considerably smaller as a percentage of initial egg mass than that of Gentoo Penguins and most other bird species. 3. 3. The generally low energetic efficiency of embryonic growth of King Penguins compared to Gentoo Penguins can be ascribed to their relatively long incubation period. 4. 4. Based on estimates of yolk composition and length of yolk formation, daily cost of egg production of King Penguins was estimated at 9.0% of basal metabolic rate (BMR) and 5.4% of BMR for the two-egg clutch of Gentoo Penguins. The relatively high cost for King Penguins largely reflects the short formation time of their eggs.

Morphometric variability on a microgeographical scale in two inshore seabirds

The range of morphometric variation among two inshore seabirds, the Kerguelen cormorant Phalacrocorax atriceps verrucosus and the gentoo penguin Pygoscelis papua was investigated on the Kerguelen and Crozet archipelagos. Four measurements (weight, culmen, flipper and body length for gentoos; weight, culmen, wing and tarsus length for cormorants) were compared in the same seven localities on Kerguelen. In addition, culmen and wing length were compared in four localities on Crozet for gentoo penguins. The two species exhibited similar trends in variation within Kerguelen although the range of variation was greater in cormorants. Compared to the largest cormorants and gentoo of Kerguelen, the smallest stocks were 60 and 36% of the weights, respectively. There is little evidence elsewhere of similar broad morphometric variability in seabirds on a microgeographical scale. The variation observed did not follow a regular cline and appeared to be less related to physical factors (sea temperatures) than to the local biological factors during the breeding season.

The breeding performance of the Gentoo Penguin Pygoscelis papua at the northern edge of its range

Gentoo Penguins Pygoscelis papua on the Crozet Islands have a unique timing of breeding, which occurs in winter and is considerably protracted, differing greatly from that of other populations breeding south of the antarctic convergence. Their breeding biology was intensively studied in 1983–1989, involving daily observations in 1983–1985. Winter breeding is associated with an extension of laying, chick rearing, foraging trips and premoult periods, a lower breeding success and a high weight loss. Annual variations in breeding performances were less pronounced than for southern populations. Variations in breeding success were closely associated with variations in feeding frequencies, fledging and breeding weight, and timing of laying. Early breeders were at an advantage over late breeders in terms of breeding success, growth patterns, fledging weight, duration of foraging trips and premoult period. The unusual winter breeding coincides with a time when food is most readily available for chick rearing in restricted foraging conditions at the edge of the species' breeding range.

The exhibit for Gentoo penguins Pygoscelis papua: at Belfast Zoo

The exhibit for Gentoo penguins Pygoscelis papua: at Belfast Zoo

Foraging parameters of gentoo penguins Pygoscelis papua at Marion Island

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.

THE WINTER DIET OF GENTOO PENGUINS AT MARION ISLAND

Summary La Cock, G. D., Hecht, T. & Klages, N. 1984. The winter diet of Gentoo Penguins at Marion Island. Ostrich 55: 188–191. The diet of Gentoo Penguins Pygoscelis papua at Marion Island was studied during September 1982. Samples were obtained from 64 birds using a stomach-pump. Fish accounted for 70% of the diet by wet weight, and crustaceans 30%. Fishes occurred in 72% of the samples, crustaceans in 75%, cephalopods in 13%, and molluscs in 8%. Cephalopods and molluscs did not form a significant proportion of any single sample. Harpagifer georgianus was the predominant fish in the diet (92,7% of otoliths recovered), and Nauticaris marionis was the only crustacean.

GEOGRAPHIC VARIATION IN GENTOO PENGUINS PYGOSCELIS PAPUA

SummaryField and museum measurements confirm the existence of a morphologically distinct southern subspecies of Gentoo Penguin Pygoscelis papua ellsworthi, breeding on the Antarctic Peninsula and the South Orkney and South Shetland Islands. Morphological and zonal differences between other island stocks are noted, but present evidence does not support further definition of subspecies.

Populations of Surface-nesting Seabirds at Marion Island, 1994/95–2002/03

During the 1990s and early 2000s, populations of surface-nesting seabirds at Marion Island showed different trends, but for the majority of species numbers decreased. Reduced numbers of gentoo penguins Pygoscelis papua, eastern rockhopper penguins Eudyptes chrysocome filholi, Crozet shags Phalacrocorax [atriceps] melanogenis and probably macaroni penguins E. chrysolophus are most plausibly attributed to an altered availability of food. Decreases in numbers of dark-mantled sooty albatrosses Phoebetria fusca, light-mantled sooty albatrosses P. palpebrata, southern giant petrels Macronectes giganteus and possibly northern giant petrels M. halli may have resulted from mortality of birds in longline fisheries. However, populations of wandering Diomedea exulans and grey-headed Thalassarche chrysostoma albatrosses fluctuated around a stable level. Numbers of Subantarctic skuas Catharacta antarctica and kelp gulls Larus dominicanus breeding at Marion Island also decreased. Kerguelen Sterna virgata and Antarctic S. vittata terns remain scarce at the island. Trends for king penguins Aptenodytes patagonicus were not reliably gauged, but numbers probably remained stable or increased. There were large fluctuations in numbers of king penguin chicks surviving to the end of winter.