1,720,997 research outputs found
Pitfalls and advances in morphometric sexing: insights from the Adélie penguin Pygoscelis adeliae
Full text linkSexing weakly/criptically dimorphic birds requires invasive techniques or molecular analysis. Alternatively, sexing can be based upon morphometric analysis, which remains invaluable in remote field conditions such as Polar regions. Nevertheless, discriminatory power may be affected by methodological issues hampering comparison between/within studies, e.g. considering alternative analytical techniques or measurements taken by different researchers. We investigated the sexing potential of bill length, bill depth and body mass in adult Adélie penguins Pygoscelis adeliae of known sex. We performed discriminant analysis on a large dataset of measurements (237 males; 264 females) taken from penguins marked between 1994 and 2001, at Edmonson Point (Ross Sea, Antarctica). In a second step, we accounted for measurements collected by different researchers through permuted discriminant analysis. We found moderate support for sex discrimination through bill measurements (77%). Considering body mass did not improve classification power substantially (78.2%), possibly because of confounding inter/intra-annual oscillations in body condition. Discriminant rate decreased when controlling the researcher effect (72.7% and 71.4%, respectively). Results were also confirmed by logistic (mixed) models. Simulations showed that reduction in sample size markedly increased uncertainty in classification power. Differences with previous studies achieving a slightly greater classification power for sexing Adélie penguins through morphometrics could be related to (i) our higher sample size and/or (ii) geographical, population-specific differences, e.g. lower degree of sexual dimorphism. Our work emphasises key-factors influencing performance of morphometric sexing in avian species, advocating population-specific validation with large sample size as well as the necessity to account for the researcher effect prior to apply morphometric sexing
Persistent organic pollutans in stomach contents of Adelie penguins from Edmonson Point (Ross Sea, Antarctica)
No full textVrije Universiteit, Amsterdam, The Netherland
Concentration and toxic evaluation of polychlorobiphenyls (PCBs) in Adelie penguin (Pygoscelis adeliae) from Edmonson Point (Ross Sea, Antarctica)
No full textSusceptibility to oxidative stress in Adelie and Emperor penguin
No full textThe antioxidant defences in aerobic organisms represent the detoxification pathway against toxicity of reactive oxygen
species (ROS). These highly reactive molecules are normally produced during the 4-electrons reduction of molecular oxygen to
water coupled with oxidative phosphorylation, and during the activity of several enzymatic systems which produce ROS as
intermediates. However, the endogenous generation of oxyradicals may be influenced by different environmental and biological
factors, and the basal efficiency of antioxidant systems generally reflects the normal prooxidant pressure to which organisms are
exposed. If the antioxidant capacity is exceeded (i.e. as a consequence of enhanced intracellular formation of ROS), a pathological
condition, generally termed oxidative stress, may arise. In this preliminary work, susceptibility to oxidative stress has been
compared in plasma of Adi lie penguin (Pygoscelis adeliae), emperor penguin (Aptenodytes forsteri), south polar skua (Catharacta
maccormicki) and snow petrel (Pagodroma nivea). Within the framework of the Italian Research Program in Antarctica, blood
samples were collected during the austral summer 1998-1999 and the Total Oxyradical Scavenging Capacity (TOSC) analysed. The
TOSC assay, measuring the capability of biological samples to neutralise different oxyradicals, has been recently standardised to
provide a quantifiable value of biological resistance to toxicity of ROS. Penguins exhibited higher scavenging capacity towards
peroxyl radicals than south polar skua and snow petrel. The greater resistance to toxicity of oxyradicals might suggest that penguins
are naturally exposed to a higher basal prooxidant pressure in comparison to other analysed Antarctic birds
Nonlinear effects of winter sea ice on the survival probabilities of Adelie penguins
No full textThe population dynamics of Antarctic seabirds are influenced by variations in winter sea ice extent and persistence; however, the type of relationship differs according to the region and the demographic parameter considered. We used annual presence/absence data obtained from 1,138 individually marked birds to study the influence of environmental and individual characteristics on the survival of Adélie penguins Pygoscelis adeliae at Edmonson Point (Ross Sea, Antarctica) between 1994 and 2005. About 25% of 600 birds marked as chicks were reobserved at the natal colony. The capture and survival rates of Adélie penguins at this colony increased with the age of individuals, and five age classes were identified for both parameters. Mean adult survival was 0.85 (SE = 0.01), and no effect of sex on survival was evident. Breeding propensity, as measured by adult capture rates, was close to one, indicating a constant breeding effort through time. Temporal variations in survival were best explained by a quadratic relationship with winter sea ice extent anomalies in the Ross Sea, suggesting that for this region optimal conditions are intermediate between too much and too little winter sea ice. This is likely the result of a balance between suitable wintering habitat and food availability. Survival rates were not correlated with the Southern Oscillation Index. Low adult survival after a season characterized by severe environmental conditions at breeding but favorable conditions during winter suggested an additional mortality mediated by the reproductive effort. Adélie penguins are sensitive indicators of environmental changes in the Antarctic, and the results from this study provide insights into regional responses of this species to variability in winter sea ice habitat. © Springer-Verlag 2009
Factors affecting thwe breeding success of the South Polar skua Catharacta mackormicki at Edmonson Point, Victoria Land, Antarctica
No full textA south polar skua (Catharacta maccormicki) population was studied at Edmonson Point (74°20′S-165°08′E), Victoria Land, Antarctica, in 1998/1999. The local population consisted of 101 pairs, 89 of which were located within a large, loose colony associated with a rookery of about 2,000 pairs of Adélie penguin (Pygoscelis adeliae). Skua nests were clumped around penguin subcolonies. Mean skua Nearest Neighbour Distance (NND) was 21 ± 15 m (n = 89). NND was positively correlated with the distance from the nearest penguin subcolony. Mean laying date was 24 ± 6 December (n = 89). Mean clutch size was 1.9 ± 0.2 eggs (n = 89). Hatching success was 77% (n = 174 eggs laid), and 20.2% of the breeding pairs successfully raised chicks to fledging. Mean number of fledged young was 0.2 ± 0.4 per breeding pair (n = 89), and 1 per successful pair (n = 18). Main causes of breeding failure were intraspecific predation and sibling aggression. Breeding success was negatively related to distance from the nearest penguin nest and to laying date. Because of the extensive and persistent sea-ice cover, penguins represented an important source of food for the skua population
Gone fishing: Adélie penguin site-specific foraging tactics and breeding performance
No full textThe ecological drivers underlying breeding performance are expected to differ across the geographical range of seabird species, but few studies have compared trade-offs between colonies with different local conditions. During chick-rearing (2000–01), we compared the foraging trips, diet and breeding parameters of two Adélie penguin colonies in the Ross Sea, at Edmonson Point (EdPo; ~2000 breeding pairs) and Inexpressible Island (InIs; ~24 000 breeding pairs). Penguins from InIs travelled farther and performed longer feeding trips. The quantity of food brought to the nest was the same for the two colonies, but penguins from InIs brought more fish and less krill. Eggs hatched earlier at EdPo. Breeding success did not differ, but chick weight during hatching–fledging was greater at InIs. Despite worse weather conditions at InIs, the larger proportion of high-energy food brought by penguins from InIs (i.e. fish) may explain their offspring‘s better performance. In addition, the persistence of fast ice at EdPo may have led to greater energy expenditure of breeding individuals, possibly reducing chick growth. The greater intraspecific competition expected at InIs may have been reduced by longer foraging trips and/or counteracted by the more nutritious diet. Our findings reveal complex trade-offs between foraging effort and environmental constraints in determining the breeding performance of Adélie penguins
Attività di ricerca e monitoraggio degli uccelli marini nell'ambito del programma Nazionale di Ricerche in Antartide
No full text
Persistent organic pollutants in some species of the Ross Sea pelagic trophic web
No full textAdélie penguin (Pygoscelis adeliae) stomach contents, krill (Euphausia superba and E. crystallorophias) and silverfish (Pleuragramma antarcticum) from the Ross Sea were analysed to determine several persistent organic pollutants (POPs). In discussing the data, the prey-predator linkage between these species was taken into account. Sampling was carried out during the 1995/96 and 1999/00 Italian Antarctic Expeditions. Fifty four polychlorobiphenyls (PCBs) andp,p'-DDE and hexachlorobenzene (HCB) were quantified in stomach contents of penguins nesting at Edmonson Point (Victoria Land) and in whole specimens of silverfish and krill from the Ross Sea. Xenobiotic concentrations in organisms were low compared to data reported for many marine species of lower latitudes and ranged from 0.22 ng g-1 wet wt p,p'-DDE in krill to 161 ng g-1 wet wt PCBs in silverfish. Fingerprints and class of isomer patterns showed a predominance of low chlorinated PCBs, mainly in pelagic organisms. Average input of these POPs through the diet was also evaluated. Concentrations of the most toxic non-ortho PCBs, IUPAC nos 77 (3,3′,4,4′), 126 (3,3′,4,4′,5) and 169 (3,3′,4,4′,5,5′), were 1.63 pg g-1 7.31 pg g-1 and 0.23 pg g-1 wet wt, respectively, in stomach content samples. Stomach contents had 0.037 pg g-1 wet wt TEQ (Toxic Equivalents) of which penta-CB 126 accounted for most of the toxicity
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