Abstract: Aim In migratory species, individuals often use fixed and individual-specific migration strategies, which we term individual migration strategy fidelity (IMSF). Our goal was to test if guillemots have flexible or fixed individual migration strategies (i.e. IMSF), if this behaviour is consistent across large parts of the genus’ range and if they were philopatric to geographical sites or a habitat feature. Location North Atlantic. Taxon Uria spp. Methods We quantified consistent individual differences in inter-annual spatial distribution and habitat occupied throughout the non-breeding period using a large geolocator tracking dataset of 729 adult seabirds breeding at 13 colonies across the Northeast Atlantic and repeatedly tracked up to 7 years over a 9-year period. Additionally, we used a similarity index to calculate relative fidelity to either geographical sites or habitats and linear mixed-effects models to assess persistence of spatial site fidelity over multiple years. Results Both guillemot species exhibited IMSF across a large part of the genus’ range which persisted over multiple years. Individuals of both species and almost all colonies showed fidelity to geographical sites and not to specific habitats. Main conclusions Guillemots show IMSF that is best explained by site familiarity (fidelity to specific sites) rather than habitat specialization (fidelity to specific habitats). In the context of rapidly changing environments, favourable habitats may permanently shift locations and hence species displaying IMSF driven by site familiarity—such as the genus Uria—may not be able to adjust their migration strategies sufficiently fast to sustain individual fitness and ensure population persistence.

Abstract: Daily Weather Regimes Are Defined Around The Kerguelen Islands (Southern Ocean) On The Basis Of Daily 500-hpa Geopotential Height Anomalies Derived From The Era5 Ensemble Reanalysis Over The Period 1979–2018. Ten Regimes Are Retained As Significant. Their Occurrences Are Highly Consistent Across Reanalysis Ensemble Members. Regimes Show Weak Seasonality And Nonsignificant Long-term Trends In Their Occurrences. Their Sequences Are Usually Short (1–3 Days), With Extreme Persistence Values Above 10 Days. Seasonal Regime Frequency Is Mostly Driven By The Phase Of The Southern Annular Mode Over Antarctica, Midlatitude Dynamics Over The Southern Ocean Such As The Pacific–south American Mode, And, To A Lesser Extent, Tropical Variability, With Significant But Weaker Relationships With El Niño–southern Oscillation. At The Local Scale Over The Kerguelen Islands, Regimes Have A Strong Influence On Measured Atmospheric And Oceanic Variables, Including Minimum And Maximum Air Temperature, Mostly Driven By Horizontal Advections, Seawater Temperature Recorded 5 M Below The Surface, Wind Speed, And Sea Level Pressure. Relationships Are Weaker For Precipitation Amounts. Regimes Also Modify Regional Contrasts Between Observational Sites In Kerguelen, Highlighting Strong Exposure Contrasts. The Regimes Allow Us To Improve Our Understanding Of Weather And Climate Variability And Interactions In This Region; They Will Be Used In Future Work To Assess Past And Projected Long-term Circulation Changes In The Southern Midlatitudes.

Abstract: Sexual competition is increasingly recognized as an important selective pressure driving species distributions. However, few studies have investigated the relative importance of interpopulation versus intrapopulation competition in relation to habitat availability and selection. To explain spatial segregation between sexes that often occurs in non-territorial and central place foragers, such as seabirds, two hypotheses are commonly used. The ‘competitive exclusion’ hypothesis states that dominant individuals should exclude subordinate individuals through direct competition, whereas the ‘niche divergence’ hypothesis states that segregation occurs due to past competition and habitat specialization. We tested these hypotheses in two populations of an extreme wide-ranging and sexually dimorphic seabird, investigating the relative role of intrapopulation and interpopulation competition in influencing sex-specific distribution and habitat preferences. Using GPS loggers, we tracked 192 wandering albatrosses Diomedea exulans during four consecutive years (2016–2019), from two neighbouring populations in the Southern Ocean (Prince Edward and Crozet archipelagos). We simulated pseudo-tracks to create a null spatial distribution and used Kernel Density Estimates (KDE) and Resource Selection Functions (RSF) to distinguish the relative importance of within- versus between-population competition. Kernel Density Estimates showed that only intrapopulation sexual segregation was significant for each monitoring year, and that tracks between the two colonies resulted in greater overlap than expected from the null distribution, especially for the females. RSF confirmed these results and highlighted key at-sea foraging areas, even if the estimated of at-sea densities were extremely low. These differences in selected areas between sites and sexes were, however, associated with high interannual variability in habitat preferences, with no clear specific preferences per site and sex. Our results suggest that even with low at-sea population densities, historic intrapopulation competition in wide-ranging seabirds may have led to sexual dimorphism and niche specialization, favouring the ‘niche divergence’ hypothesis. In this study, we provide a protocol to study competition within as well as between populations of central place foragers. This is relevant for understanding their distribution patterns and population regulation, which could potentially improve management of threatened populations.

Abstract: Advances in biologging technology have enabled 3D dead-reckoning reconstruction of marine animal movements at spatiotemporal scales of meters and seconds. Examining high-resolution 3D movements of sharks (Galeocerdo cuvier, N = 4; Rhincodon typus, N = 1), sea turtles (Chelonia mydas, N = 3), penguins (Aptenodytes patagonicus, N = 6), and marine mammals (Arctocephalus gazella, N = 4; Ziphius cavirostris, N = 1), we report the discovery of circling events where animals consecutively circled more than twice at relatively constant angular speeds. Similar circling behaviors were observed across a wide variety of marine megafauna, suggesting these behaviors might serve several similar purposes across taxa including foraging, social interactions, and navigation.

Abstract: Since The Signature Of The Minamata Convention On Mercury In 2017, National Regulation Coordinated At An International Level Will Come Into Force In Order To Limit Anthropogenic Emissions And Therefore Protect The Human Health And Ecosystem From This Highly Toxic Pollutant. One Need To Evaluate The Efficiency Of National Measures, And Long-term Monitoring Of Atmospheric Mercury (Hg) Is An Important Tool To Address The Changes Over Time Of Emission Sources, Transport, And Deposition Patterns.the Global Mercury Observation System (Gmos) Project Was Funded By The European Commission (Http://www.gmos.eu) And Started In November 2010 With The Overall Goal To Develop A Coordinated Global Observing System To Monitor Hg On A Global Scale, Including A Large Network Of Ground-based Monitoring Stations. To Date, More Than 40 Ground-based Monitoring Sites Constitute The Global Network Covering Many Regions Where Little To No Observational Data Were Available Before Gmos (Sprovieri Et Al., 2016). All Gmos Work Is Now Continued In The Framework Of The International Frame Work Of Gos4m (Global Observation System For Mercury – Http://www.gos4m.org)although Essential To Fully Understand The Cycling Of Mercury At The Global Scale, Mercury Species Records In The Southern Hemisphere Were Really Scarce Before Gmos. In This Context, An Atmospheric Mercury Monitoring Station Has Been Set Up On Amsterdam Island (37◦48 S, 77◦34 E) In The Remote Southern Indian Ocean In 2012. Since 2012, We Continuously Measured Gaseous Mercury Species With A 15 Min Frequency. Angot Et Al. (2014) Discussed The First Two Years Of This Record, Using Principally Wind Sector Analysis And Air Mass Back Trajectories. They Also Include In Their Analysis The Unique Continuous Record Of Radon 222 And 220 (Thoron) (Polian Et Al., 1986; Kritz Et Al., 1990). Radon 222 And 220 (Thoron) Activities Can Be Used To Distinguish Local Soil Outgassing From Remote Continental Source. Combined With Meteorological Data, The Change Of Activities Are Then Powerful Tool To Classify Air Mass Origin For The Atmospheric Gaseous Mercury Record. Rapid And Sharp Variations Of Radon 222 Activity, Referred To As &Ldquo;radonic Storms” (Lambert Et Al., 1970) And Ascribed To Strong Continental Air Mass Advection, Are Then Observed At Amsterdam Island. The Occurrence Of Radonic Storms Was Estimated To Be About 4 % In 2012 And 7 % In 2013. Considering The Works Realized In 2014, The Goal Of This Internship Is To Deeper Explore The Relationships Between The Collected Gaseous Elemental Mercury And Observed Radon (222rn / 220rn) Activities In The Entire Data Set. In Particular, We Will Study The Specific And Coupled Trend Of These Compounds, The Frequency And Intensity Of Radonic Storm Occurrence And Their Potential Link With The Gaseous Elemental Mercury Cycle. Local Meteorology Data As Well As Backtrajectories Simulation (Hysplit And/or Flexpart Model) Will Be Also Used.