Abstract: Hormones are a link between environmental stimuli and the behavioural and/or
physiological responses of organisms. The release of corticosterone (hereafter CORT) has
major effects on both energy mobilization and its allocation among the various requirements
of an individual. However, specific effects of CORT on behaviours related to energy
acquisition and, consequently, its allocation with regards to survival and reproduction, are
complex and remain to be deciphered at a fine scale. We examined here the effects of elevated
baseline CORT levels on this trade-off through a detailed study of foraging behaviour in the
Adélie penguin (Pygoscelis adeliae) during the chick-rearing stage. We monitored the at-sea
behaviour of CORT-implanted and control male birds using time-depth recorders, and
monitored the effects of CORT treatment on their body conditions, as well as their chicks’
body masses and survival. Bio-logged data were examined via both traditional measures of
diving behaviour and fractal analysis as an index of behavioural complexity. At the level of
the foraging trip, CORT administration led to a transient decrease in overall foraging effort
(i.e. reductions in the duration of at-sea trips, the time spent diving and the number of dives
performed) as well as the complexity with which treated birds foraged. In contrast, per-dive
performance indices suggest an increase in both efficiency and prey pursuit rates. These
contrasting results suggest the importance of assessing diving behaviour at scales
encompassing both entire foraging trips, as well as individual dives. Ultimately, however, we
observed no short-term effects of treatment on either adult body condition or on chick body
mass and survival. We conclude that under conditions of energy constraint, as mimicked by
our experimental paradigm, sequences of behaviour may become more structured and
periodic as observed in CORT-treated birds. The increased dive-scale effort observed in
CORT-birds could then be a strategy allowing a reduction in trip-scale effort. Indeed, the
increased CORT levels may have forced treated penguins to revert to mechanisms preserving
their survival by engaging in less costly foraging behaviours. This study highlights the utility
of using both traditional and fractal analyses to better understand the responses of free-living
animals to energetic challenges and various environmental constraints.

Abstract: Investigating the foraging ecology of seabirds is especially challenging given their wide-ranging movements and the practical difficulties of obtaining unbiased information on their feeding behavior. Despite the development of animal-borne tracking devices, several limitations preclude investigations at the scale of a whole community in a given season or year, and, until recently, during the non-breeding period. Here we analyzed δ¹³C and δ¹⁵N in feathers of chicks and adults to investigate inter- and intra-specific variation in the foraging habitat and trophic position of 9 large procellariiform seabirds from 6 southern breeding localities during the breeding and non-breeding periods. Isotopic ratios of each species were generally consistent among different breeding populations, despite the large geographical scale and potential variation in oceanography in surrounding waters. Both spatial and trophic segregation apparently allowed the co-existence of sympatric species in most breeding localities, except at South Georgia, where both δ¹³C and δ¹⁵N in chicks showed high overlap among species, probably resulting from the superabundance of alternative food resources during the summer. Low variance in stable isotope ratios among adults in several species indicated high overlap between individuals in feeding habits and trophic levels (i.e. isotopic specialist populations) during the non-breeding period. By contrast, large isotopic variances and the high within- and between-individual components of the trophic niche width suggested that grey-headed and light-mantled sooty albatrosses are generalists. Based on δ¹³C, the species that breed in the Southern Ocean can be categorized as residents or subtropical migrants, with the latter including oceanic and neritic subtropical migrants. Albatrosses meet the high energetic challenge of feather synthesis by foraging in different habitats, depending on the length of the non-breeding period. Annual breeders renew their plumage in productive neritic waters in ~4 mo, whereas biennially breeding species moult in less productive oceanic waters over much longer periods (~12 to 16 mo).

Abstract: ABSTRACT: Recent observations on the western Antarctic Peninsula have suggested that changing climatic conditions may be increasing pressure on breeding seabirds due to higher exploitation rates by the tick Ixodes uriae. Using data from 8 microsatellite markers and ticks from 6 Pygoscelis spp. colonies, we employed a population genetics approach to specifically test the hypothesis that I. uriae is expanding south-westward along the peninsula from the Subantarctic region. Contrary to expectations, tick genetic diversity was high within all colonies, and no remaining signal of colonisation events was evident. Although significant geographic genetic structure occurred among ticks from different colonies, these ectoparasites tended to belong to 2 major genetic groups, one found principally in south-western locations (Palmer Station area) and the other in more north-eastern areas (South Shetland Islands). More central colonies showed a mixture of ticks from each genetic group, suggesting that this area represents a hybridisation zone of ticks from 2 distinct origins. A subsequent clustering analysis, including ticks from 2 Subantarctic locations, did not reveal the source population for the northern peninsula group. Overall, our data refute the hypothesis of a recent south-westward expansion of I. uriae along the peninsula and suggest that this tick has been present at more southern latitudes for an extended period of time. Further studies on the distribution and genetic characteristics of this ectoparasite around Antarctica are now required to better understand the colonisation process and predict how changing environmental conditions may affect its presence and diversity in seabird colonies.

Abstract: Over the last century, major climate changes and intense human exploitation of natural living resources have occurred in the Southern Ocean, potentially affecting its ecosystems up to top marine predators. Fisheries may also directly affect seabirds through bycatch and additional food resources provided by discards. The past 20 yr of research has seen an increasing number of studies investigating the effects of climate change and fisheries activities on Southern Ocean seabirds. Here, we review these studies in order to identify patterns in changes in distribution, phenology, demography and population dynamics in response to changes in climate and fisheries bycatch. Shifts in distribution and breeding phenology were documented in parallel to increases in sea-surface temperatures and changes in sea-ice cover. Above all warm sea-surface temperatures negatively affected demographic parameters, although exceptions were found. Relationships suggest non-linear effects of sea-ice cover on demographic parameters and population dynamics, with optimum sea-ice cover conditions appearing to be the rule. Fishing efforts were mainly negatively related to survival rates, and only for a few species positively related to breeding success. A handful of studies found that chronic mortality of immature birds due to fisheries negatively affected populations. Climate factors and fisheries bycatch may simultaneously affect demographic parameters in a complex way, which can be integrated in population models to project population trajectories under future climate or fisheries scenarios. Needed are studies that integrate other environmental factors, trophic levels, foraging behaviour, climate−fisheries interactions, and the mechanisms underlying phenotypic plasticity, such as some pioneering studies conducted elsewhere.

Abstract: With technical advances in wildlife telemetry, the study of cryptic predators’ responses to prey distribution has been revolutionised. In the case of marine predators, high resolution tagging devices have been developed recently to collect precise diving datasets covering extended periods of time. In this study, we investigated changes in the horizontal movements and diving patterns of a marine predator, the southern elephant seal, at fine temporal and spatial scales. Satellite tracking data collected for 9 seals were processed with switching state-space models. Seal body condition, as a proxy for foraging success, was estimated through changes in drift rate from Time Depth Recorder (TDR) data. We identified (1) statistically distinct behavioural modes from the tracking data (intensive vs. extensive foraging modes) and (2) distinct dive classes from the TDR diving data (drift, exploratory, shallow active and deep active dives). Active dives, associated with vertical foraging and chasing, were more numerous when the seals were in intensive foraging mode. Improved body condition and mass gain of seals were also associated with the intensive foraging mode and, within the vertical dimension, with sets of highly active dives. In conclusion, proportions of dive classes varied according to seals’ horizontal behaviour. Intensive foraging detected from surface tracking data is a good predictor of diving activity and foraging success occurring in the vertical dimension.