Abstract: Most birds incubate their eggs, which requires time and energy at the expense of other activities. Birds generally have two incubation strategies: biparental where both mates cooperate in incubating eggs, and uniparental where a single parent incubates. In harsh and unpredictable environments, incubation is challenging due to high energetic demands and variable resource availability. We studied the relationships between the incubation behaviour of sandpipers (genus Calidris) and two environmental variables: temperature and a proxy of primary productivity (i.e. NDVI). We investigated how these relationships vary between incubation strategies and across species among strategies. We also studied how the relationship between current temperature and incubation behaviour varies with previous day's temperature. We monitored the incubation behaviour of nine sandpiper species using thermologgers at 15 arctic sites between 2016 and 2019. We also used thermologgers to record the ground surface temperature at conspecific nest sites and extracted NDVI values from a remote sensing product. We found no relationship between either environmental variables and biparental incubation behaviour. Conversely, as ground-surface temperature increased, uniparental species decreased total duration of recesses (TDR) and mean duration of recesses (MDR), but increased number of recesses (NR). Moreover, small species showed stronger relationships with ground-surface temperature than large species. When all uniparental species were combined, an increase in NDVI was correlated with higher mean duration, total duration and number of recesses, but relationships varied widely across species. Finally, some uniparental species showed a lag effect with a higher nest attentiveness after a warm day while more recesses occurred after a cold day than was predicted based on current temperatures. We demonstrate the complex interplay between shorebird incubation strategies, incubation behaviour, and environmental conditions. Understanding how species respond to changes in their environment during incubation helps predict their future reproductive success.

Abstract: Qikirtajuaq is a long island facing the Inuit village of Akulivik on the northeastern coast of Hudson Bay (Canada) that is rich in archaeological sites. Kangiakallak-1 (JeGn-2), one of the main sites on this island, is a large multicomponent site that includes Dorset and Thule Inuit winter houses. This study documents the dynamics of palaeoenvironmental conditions in the successive occupations of the Kangiakallak-1 settlement based on plant macrofossils, pollen and non-pollen palynomorph analyses and archaeological research. The data indicate that Dorset inhabitants constructed their dwelling at about 772 cal. a BP. The site was reused by the Thule Inuit a few decades later, starting at about 671 cal. a BP. Thus, Kangiakallak-1 is one of the few sites, at least in Nunavik (northern Quebec, Canada), that were rapidly reoccupied by the Thule Inuit after the departure of the Dorset inhabitants, which indicates a possible overlap between the two cultures in the Akulivik region. The palaeoecological data show that both Dorset and Thule inhabitants left clear footprints at the local scale in the form of several nitrophilous species that became established in and near the houses and persisted over a long period. The deposition of domestic waste (including bone fragments, skin, burnt fat and charcoal fragments) inside the subterranean dwellings fertilized the soil and led to the growth of unique nitrophilous plants. These changes transformed the houses into exceptional floristic refuges.

Abstract: The Patagonian slope is the region where Subantarctic waters and bathymetry give raise to physical and ecological processes that support a rich biodiversity and a large-scale industrial fisheries. Unique among the species that depend on this region is the deep diving southern elephant seal, Mirounga leonina. We report here on changes in the foraging behavior of a female seal explained by the combined effect of a cold and high salinity water mass and a decrease in surface chlorophyll-a concentration. Behavioral and oceanographic data from about 5000 profiles of temperature, conductivity, pressure, light and prey encounters were collected within an area ranging 59.5–61°W and 46–47.5°S, at depths of 300–700 m, on the Patagonian slope, during November–December 2018. A decrease in temperature (0.15 °C) and an increase in salinity (0.03) was found below the mixed layer, during December. Light data revealed a significant increase of irradiance in December (almost reaching the ocean bottom) associated with a decrease of chlorophyll-a in the upper levels. Concomitantly, the seal had a different diving behavior in December, foraging near the surface at night and close to the bottom during daylight hours. Also, the seal doubled the prey capture attempts in December compared to November. This study reveals the importance of ocean physical properties on seal's diving and foraging behavior, and how this changes, although small, can impact on seals diet and body composition during their post-breeding trips.

Abstract: De nombreuses questions restent en suspens quant aux relations existantes entre les processus biologiques et physiques dans l'océan Austral. Pour répondre à ces questions, des enregistreurs électroniques sont déployés sur des prédateurs marins, et notamment sur des éléphants de mer austraux. Ces enregistreurs échantillonnent une grande variété de données physiques, biologies ou comportementales à haute fréquence générant ainsi une quantité considérable d’information. L’ensemble de ces données sont dites fonctionnelles car elles présentent un caractère commun : elles évoluent selon un continuum, qu’il soit spatial ou temporel. L’objectif de cette thèse est donc double, il s’agit d’étudier l’activité alimentaire de femelles éléphant de mer en relation avec les processus physiques de l’océan austral, tout en intégrant le caractère fonctionnel des données échantillonnées. Les résultats obtenus montrent que (1) par rapport aux méthodes classiquement employées, les méthodes d’analyse de données fonctionnelles permettent d’identifier une plus grande variété de comportements de plongées au sens biologique défini. (2) Ces approches fonctionnelles sont plus adaptées pour des données aux fréquences d’échantillonnage variable. (3) L’analyse de données fonctionnelles nous permet également d’accéder à la densité de nos individus, reflet de leur condition corporelle, et les comportements de plongées qu’ils adoptent ont une influence réelle sur cette condition corporelle, à différentes échelles de temps. (4) Il existe une relation entre les caractéristiques des masses d’eau rencontrées par les femelles éléphants de mer et les plongées qu’elles effectuent.

Abstract: We use the am, an, as and the aσ geomagnetic indices to the explore a previously overlooked factor in magnetospheric electrodynamics, namely the inductive effect of diurnal motions of the Earth’s magnetic poles toward and away from the Sun caused by Earth’s rotation. Because the offset of the (eccentric dipole) geomagnetic pole from the rotational axis is roughly twice as large in the southern hemisphere compared to the northern, the effects there are predicted to be roughly twice the amplitude of those in the northern hemisphere. Hemispheric differences have previously been discussed in terms of polar ionospheric conductivities generated by solar photoionization, effects which we allow for by looking at the dipole tilt effect on the time-of-year variations of the indices. The electric field induced in a geocentric frame is shown to also be a significant factor and gives a modulation of the voltage applied by the solar wind flow in the southern hemisphere that is typically a ±30% diurnal modulation for disturbed intervals rising to ±76% in quiet times. For the northern hemisphere these are 15% and 38% modulations. Motion away from/towards the Sun reduces/enhances the directly-driven ionospheric voltages and reduces/enhances the magnetic energy stored in the tail and we estimate that approximately 10% of the effect appears in directly driven ionospheric voltages and 90% in changes of the rate of energy storage or release in the near-Earth tail. The hemispheric asymmetry in the geomagnetic pole offsets from the rotational axis is shown to be the dominant factor in driving Universal Time (UT) variations and hemispheric differences in geomagnetic activity. Combined with the effect of solar wind dynamic pressure and dipole tilt on the pressure balance in the near-Earth tail, the effect provides an excellent explanation of how the observed Russell-McPherron pattern with time-of-year F and UT in the driving power input into the magnetosphere is converted into the equinoctial F-UT pattern in average geomagnetic activity (after correction is made for dipole tilt effects on ionospheric conductivity), added to a pronounced UT variation with minimum at 02–10 UT. In addition, we show that the predicted and observed UT variations in average geomagnetic activity has implications for the occurrence of the largest events that also show the nett UT variation.