Abstract: In altricial species, parents brood their chicks constantly before leaving them unattended sometimes for extended periods when they become thermally independent. During this second phase, there is sometimes important inter-individual differences in parental attendance and the fitness costs and benefits of parental strategies have previously been extensively investigated. However, the impact of parental presence on offspring behaviors and stress physiology has been overlooked. Here, we examined the influence of parental presence on offspring hormonal and behavioral stress sensitivities in snow petrel chicks. We demonstrated for the first time in a wild bird species that attended chicks had lower stress-induced corticosterone levels and a lower probability to show defensive behavior compared to the alone chicks. This reduced stress sensitivity is certainly explained by the well-known link between corticosterone and nutritional status, and by the recent delivery of meals to the attended chicks and the improvement of their nutritional status. It may also be explained by the parental protection against predators or inclement weather, or/and by the psychosocial comfort of parental presence for the offspring. Overall, these results suggest that the presence of a parent in the nest reduces offspring stress sensitivity in wild birds. Further studies would now be required to disentangle the impact of nutritional status and parental presence on stress sensitivity and to better understand the potential impact of parental presence and circulating corticosterone levels on growth and cognitive development in wild birds.

Abstract: The first year of life is a period of high mortality in animals. Reduced foraging capacities of naive individuals might be the primary cause of their mortality. These capacities are supposed to be progressively acquired during the first months of life. In this study, we investigate the ontogeny of flight capacities, by day and night, of first-year individuals, and compare it with adults from two closely related species of great albatrosses: Amsterdam Diomedea amsterdamensis and wandering Diomedea exulans albatrosses which forage in different environmental conditions. We used 71 tracks of 71 juvenile birds and 141 of 116 incubating adults to compare both age categories. In order to explore the effect of moon light on night activity, we elaborated a new formula which improves the precision of the proxy of moon illumination. By day, we found that juveniles of both species reach some adult foraging capacities in less than two months. By night, albatrosses have reduced activity increasing during the first weeks at sea for juveniles and changing in accordance with moon illumination for both juveniles and adults. A peak of flight activity at dawn and dusk was apparent for both species. Interspecific comparison underlined that Amsterdam albatrosses were more active than wandering albatrosses, suggesting a difference in food and foraging strategy. Overall, we highlighted how life history traits, environmental conditions and time of the day affect the foraging activity of two related species of seabirds.

Abstract: Capital breeders accumulate nutrients prior to egg development, then use these stores to support offspring development. In contrast, income breeders rely on local nutrients consumed contemporaneously with offspring development. Understanding such nutrient allocations is critical to assessing life-history strategies and habitat use. Despite the contrast between these strategies, it remains challenging to trace nutrients from endogenous stores or exogenous food intake into offspring. Here, we tested a new solution to this problem. Using tissue samples collected opportunistically from wild emperor penguins Aptenodytes forsteri, which exemplify capital breeding, we hypothesized that the stable carbon (δ13C) and nitrogen (δ15N) isotope values of individual amino acids (AAs) in endogenous stores (e.g. muscle) and in egg yolk and albumen reflect the nutrient sourcing that distinguishes capital versus income breeding. Unlike other methods, this approach does not require untested assumptions or diet sampling. We found that over half of essential AAs had δ13C values that did not differ between muscle and yolk or albumen, suggesting that most of these AAs were directly routed from muscle into eggs. In contrast, almost all non-essential AAs differed in δ13C values between muscle and yolk or between muscle and albumen, suggesting de novo synthesis. Over half of AAs that have labile nitrogen atoms (i.e. ‘trophic’ AA) had higher δ15N values in yolk and albumen than in muscle, suggesting that they were transaminated during their routing into egg tissue. This effect was smaller for AAs with less labile nitrogen atoms (i.e. ‘source’ AA). Our results indicate that the δ15N offset between trophic-source AAs (Δ15Ntrophic-source) may provide an index of the extent of capital breeding. The value of emperor penguin Δ15NPro-Phe was higher in yolk and albumen than in muscle, reflecting the mobilization of endogenous stores; in comparison, the value of Δ15NPro-Phe was similar across muscle and egg tissue in previously published data for income-breeding herring gulls Larus argentatus smithsonianus. Our results provide a quantitative basis for using AA δ13C and δ15N, and isotopic offsets among AAs (e.g. Δ15NPro-Phe), to explore the allocation of endogenous versus exogenous nutrients across the capital versus income spectrum of avian reproduction.

Abstract:

Abstract. The lower-thermosphere–ionosphere (LTI) system consists of the upper atmosphere and the lower part of the ionosphere and as such comprises a complex system coupled to both the atmosphere below and space above. The atmospheric part of the LTI is dominated by laws of continuum fluid dynamics and chemistry, while the ionosphere is a plasma system controlled by electromagnetic forces driven by the magnetosphere, the solar wind, as well as the wind dynamo. The LTI is hence a domain controlled by many different physical processes. However, systematic in situ measurements within this region are severely lacking, although the LTI is located only 80 to 200 km above the surface of our planet. This paper reviews the current state of the art in measuring the LTI, either in situ or by several different remote-sensing methods. We begin by outlining the open questions within the LTI requiring high-quality in situ measurements, before reviewing directly observable parameters and their most important derivatives. The motivation for this review has arisen from the recent retention of the Daedalus mission as one among three competing mission candidates within the European Space Agency (ESA) Earth Explorer 10 Programme. However, this paper intends to cover the LTI parameters such that it can be used as a background scientific reference for any mission targeting in situ observations of the LTI.

Abstract: The atmospheric cosmic-ray environment is composed of secondary particles produced when primary cosmic rays interact with the nucleus of atmospheric atoms. Modeling of atmospheric radiations is essential for investigating their impacts on human activities such as radiation risks in aviation or scientific fields such as cosmogenic dating. The nuclear transport codes are a common and accurate way to model the cosmic ray interaction in the atmosphere with minimal approximations. However, tracking all produced secondary particles in each event in the whole depth of the atmosphere and sampling many events to obtain the statistically meaningful results would be a computational challenge and disadvantageous from the point of view of time consumption. This paper presents a computational platform names ATMOS CORE based on pre-calculated databases coupled to physical models and computational methods. The fields of application concern the atmospheric cosmic-rays characterization as well as their effects on electronics systems, on the ambient dose for aircrews or the cosmogenic nuclide production for dating activities. Some comparisons between simulations and measurements are also presented and discussed.