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Poisbleau M.,Max Planck Institute for Ornithology (Radolfzell) | Poisbleau M.,University of Antwerp | Demongin L.,Max Planck Institute for Ornithology (Radolfzell) | Strange I.J.,New Island Conservation Trust | And 2 more authors.
Journal of Ornithology | Year: 2011

Crested penguins (genus Eudyptes) present a unique reversed egg-size dimorphism and hatching asynchrony, with the larger second-laid egg (B-egg) hatching before the smaller first-laid egg (A-egg). Both a higher water vapour conductance and parental favouritism during incubation could explain the shorter incubation period for the B-egg than for the A-egg. Because the incubation period is increased by the presence of a sibling for A-eggs, but not for B-eggs, and because both egg categories have the same incubation period when they are incubated alone, it has been suggested that the difference in incubation period was largely driven by the parental favouritism for B-eggs during incubation. We tested whether A- and B-eggs show a difference in laying density, density at the beginning of incubation and in density decrease during incubation according to the presence of a sibling. Although density at the start of incubation was significantly higher for B-eggs than for A-eggs, the decrease in density during incubation had the same slope for both egg categories. Moreover, the presence of a sibling did not influence densities. We additionally provide two equations that allow the back-dating of laying dates for a clutch of SouthernRockhopper Penguin (Eudyptes c. chrysocome) and we discuss the precision of the method (3.04 ± 2.29 days for A-eggs and 2.73 ± 2.10 days for B-eggs) for penguins which are increasingly being used as marine environmental sentinels. © 2010 Dt. Ornithologen-Gesellschaft e.V. Source


Poisbleau M.,Max Planck Institute for Ornithology (Radolfzell) | Poisbleau M.,University of Antwerp | Demongin L.,Max Planck Institute for Ornithology (Radolfzell) | Demongin L.,University of Antwerp | And 3 more authors.
Ardea | Year: 2010

Following recent phylogenetic work, Rockhopper Penguins were suggested to consist of two or three species. For the Southern Rockhopper Penguin Eudyptes c. chrysocome, sexual dimorphism has not been studied in detail, and only a few previous studies on penguins have investigated sexual dimorphism in immatures and chicks. Using data in the literature, we examined whether the sexual dimorphism of adults varies among the three taxa of Rockhopper Penguins and then we investigated the most reliable measurements to sex adult Rockhopper Penguins. We observed that bill length is the most useful measurement to separate males from females. To allow for sex discrimination In the field, we also examined a large dataset of Southern Rockhopper Penguins from New Island, Falkland Islands, including adults sexed via observation of behaviour, and immatures and chicks sexed genetically. We found that male adults and immatures were larger than females in bill length and bill depth and, to a lesser degree, in flipper lengths. We thus derived discriminant functions from bill length and bill depth and correctly sexed 96.2% of adults and 91.8% of immatures. In newly hatched chicks, males had a longer bill than females, but sexing was only successful for 63.5% of hatchlings. Just before the crèche age (18 and 19 days) and after the pre-fledging moult (55 days and older), all morphological measurements of chicks were significantly different between sexes, and sex determination was successful for 68.2% and 84.3% of chicks in these age groups, respectively. Consistently among age groups, bill length was the most dimorphic character in this population. Source


Demongin L.,Max Planck Institute for Ornithology (Radolfzell) | Poisbleau M.,Max Planck Institute for Ornithology (Radolfzell) | Poisbleau M.,University of Antwerp | Rey A.R.,CONICET | And 4 more authors.
Polar Biology | Year: 2010

All crested penguins present a unique reversed hatching asynchrony: the larger second-laid egg (B-egg) hatches before the smaller first-laid egg (A-egg). Although both eggs often hatch, the A-chick generally dies of starvation within days after hatching. However, within rockhopper penguins, the population at the Falkland Islands is unique in that some birds manage to raise both chicks. Although it has been suggested that the egg size dimorphism between A- and B-eggs may explain how long both eggs and chicks survive, this hypothesis has never been explicitly tested. We expect that both eggs are retained longer in the less dimorphic clutches than in the more dimorphic ones. In this paper, we have compiled egg measurements for three rockhopper penguin species (Eudyptes chrysocome, E. filholi and E. moseleyi) in order to compare the intra-clutch egg size dimorphism among these species. Furthermore, we have collected new data to compare egg size dimorphism between two populations of E. chrysocome (Falkland Islands versus Staten Island). A-egg volumes are more variable between species and populations than B-egg volumes. E. chrysocome and especially the population from the Falkland Islands produces the largest A-eggs and the least dimorphic eggs. Nevertheless, as differences in A-egg volumes between species and between the populations of Falkland Islands and Staten Island are stronger and more significant than differences in egg dimorphism, we suggest that A-egg volume, more than egg dimorphism, could be one of the factors influencing the prevalence of twins. A large A-egg and/or reduced egg dimorphism is probably necessary to enable rockhopper penguins to raise two chicks, but other reasons may also be involved which enable them to keep both eggs and chicks. © 2009 The Author(s). Source


Demongin L.,Max Planck Institute for Ornithology (Radolfzell) | Poisbleau M.,Max Planck Institute for Ornithology (Radolfzell) | Poisbleau M.,University of Antwerp | Strange G.,New Island Conservation Trust | Strange I.J.,New Island Conservation Trust
Wilson Journal of Ornithology | Year: 2010

The Snares Penguin (Eudyptes robustus) breeds only on the Snares Islands, New Zealand, and is vagrant throughout the New Zealand region and southeast Australia. The only previous record outside this area was one in the Falkland Islands in 1988. We report the unusual occurrence of two Snares Penguins in the same colony in the Falkland Islands in 2008, and discuss identification issues. Vagrant penguins demonstrate the incredible dispersal ability of these flightless birds. © 2010 by the Wilson Ornithological Society. Source


Quillfeldt P.,Max Planck Institute for Ornithology (Radolfzell) | Michalik A.,Max Planck Institute for Ornithology (Radolfzell) | Michalik A.,University of Osnabruck | Veit-Kohler G.,Senckenberg Institute | And 2 more authors.
Marine Biology | Year: 2010

Central place foragers are constrained in their foraging distribution by the necessity to return to their nest site at regular intervals. In many petrels that feed on patchily distributed prey from the sea surface over large foraging areas, alternating long and short foraging trips are used to balance the demands of the chick with the requirements of maintaining adult body condition. When the local conditions are favourable for prey density and quality, adults should be able to reduce the number of long foraging trips. We studied the flexibility in foraging trip lengths of a small pelagic petrel, the thin-billed prion Pachyptila belcheri, over three breeding seasons with increasingly favourable, cold-water conditions. During a warm-water influx in February 2006, chicks were fed less frequently and adults carried out foraging trips of up to 8 days. When conditions became more favourable with colder water temperatures in 2007 and 2008, thin-billed prions decreased trip lengths, more often attended their chick every day, and long foraging trips of six to eight days were not registered during 2008. Chick growth rates mirrored this, as chicks grew poorly during 2006, intermediate during 2007 and best during 2008. Thin-billed prions preyed mainly on squid during incubation and mainly on amphipods and euphausiids during chick-rearing. In the poorest season only, the diet was substantially supplemented with very small copepods. Together, the present results indicate that during warm-water conditions, thin-billed prions had difficulties in finding sufficient squid, amphipods or euphausiids and were forced to switch to lower trophic level prey, which they had to search for over large ocean areas. © 2010 Springer-Verlag. Source

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