Interspecific competition impacts the occupancy and range limits of two ptarmigan species along the elevation gradient in Norway

Many mountain species are expected to respond to climate change through upslope shifts of their range limits, but competition may restrict or alter this response. Under traditional range-limit theory, it is expected that lower-elevation species are better competitors than closely related higher-elevation species. However, recent work finds that this prediction is often unmet. We investigated evidence for the impact of competition during breeding season on the elevational range limits of a pair of closely related bird species, willow ptarmigan Lagopus lagopus and rock ptarmigan L. muta, in mainland Norway. The species share overlapping ranges that loosely divide slightly upslope from the treeline ecotone, with willow ptarmigan generally occupying lower sites and rock ptarmigan occupying higher sites. We used multi-species occupancy models to test four competing hypotheses for how competition may affect the range limit between willow ptarmigan and rock ptarmigan: 1) asymmetric competition that restricts the lower range limit of rock ptarmigan; 2) asymmetric competition that restricts the upper range limit of willow ptarmigan; 3) condition-specific competition that restricts both species’ range limits; and 4) range limits unaffected by competition. We found evidence for a negative pairwise interaction between the two species. Changes in interaction strength along the elevation gradient suggested evidence for condition-specific competition. However, a strong positive correlation between rock ptarmigan and higher-elevation habitat resulted in a highly asymmetric outcome, where the upper range limit of willow ptarmigan was restricted but rock ptarmigan occupancy was fairly independent of willow ptarmigan. This outcome is opposite to the prediction of traditional range-limit theory and may suggest a greater climate threat to willow ptarmigan than has been previously projected. Thus, our results demonstrate the importance of considering biotic interactions at both the higher and lower ends of species’ range limits along elevation gradients. elevation gradient, interspecific competition, occupancy, ptarmigan, range limitspublishedVersio

An assessment of relative habitat use as a metric for species' habitat association and degree of specialization

Corrigendum: Ecological Indicators, Volume 137, April 2022, Article number 108627, https://doi.org/10.1016/j.ecolind.2022.108627.In order to understand species' sensitivity to habitat change, we must correctly determine if a species is associated with a habitat or not, and if it is associated, its degree of specialization for that habitat. However, definitions of species' habitat association and specialization are often static, categorical classifications that coarsely define species as either habitat specialists or generalists and can fail to account for potential temporal or spatial differences in association or specialization. In contrast, quantitative metrics can provide a more nuanced assessment, defining species' habitat associations and specialization along a continuous scale and accommodate for temporal or spatial variation, but these approaches are less widely used. Here we explore relative habitat use (RHU) as a metric for quantifying species' association with and degree of specialization for different habitat types. RHU determines the extent of a species' association with a given habitat by comparing its abundance in that habitat relative to its mean abundance across all other habitats. Using monitoring data for breeding birds across Europe from 1998 to 2017; we calculate RHU scores for 246 species for five habitat types and compared them to the literature-based classifications of their association with and specialization for each of these habitats. We also explored the temporal variation in species' RHU scores for each habitat and assessed how this varied according to association and degree of specialization. In general, species' RHU and literature-derived classifications were well aligned, as RHU scores for a given habitat increased in line with reported association and specialization. In addition, temporal variation in RHU scores were influenced by association and degree of specialization, with lower scores for those associated with, and those more specialized to, a given habitat. As a continuous metric, RHU allows a detailed assessment of species' association with and degree of specialization for different habitats that can be tailored to specific temporal and/or spatial requirements. It has the potential to be a valuable tool for identifying indicator species and in supporting the design, implementation and monitoring of conservation management actions.Peer reviewe

Arctic avian predators synchronise their spring migration with the northern progression of snowmelt

Migratory species display a range of migration patterns between irruptive (facultative) to regular (obligate), as a response to different predictability of resources. In the Arctic, snow directly influences resource availability. The causes and consequences of different migration patterns of migratory species as a response to the snow conditions remains however unexplored. Birds migrating to the Arctic are expected to follow the spring snowmelt to optimise their arrival time and select for snow-free areas to maximise prey encounter en-route. Based on large-scale movement data, we compared the migration patterns of three top predator species of the tundra in relation to the spatio-temporal dynamics of snow cover. The snowy owl, an irruptive migrant, the rough-legged buzzard, with an intermediary migration pattern, and the peregrine falcon as a regular migrant, all followed, as expected, the spring snowmelt during their migrations. However, the owl stayed ahead, the buzzard stayed on, and the falcon stayed behind the spatio-temporal peak in snowmelt. Although none of the species avoided snow-covered areas, they presumably used snow presence as a cue to time their arrival at their breeding grounds. We show the importance of environmental cues for species with different migration patterns

Legacy and emerging organohalogenated compounds in feathers of Eurasian eagle-owls (Bubo bubo) in Norway: Spatiotemporal variations and associations with dietary proxies (δ13C and δ15N)

The occurrence of organohalogenated compounds (OHCs) in wildlife has received considerable attention over the last decades. Among the matrices used for OHCs biomonitoring, feathers are particularly useful as they can be collected in a minimally or non-invasive manner. In this study, concentrations of various legacy OHCs –polychlorinated biphenyls (PCBs), organochlorine pesticides (OCPs) and polybrominated diphenyl ethers (PBDEs)–, as well as emerging OHCs –per- and polyfluoroalkyl substances (PFAS) and organophosphate ester flame retardants (OPEs)– were determined in feathers of 72 Eurasian eagle-owls (Bubo bubo) from Norway, with the goal of studying spatiotemporal variation using a non-invasive approach. Molted feathers were collected at nest sites from northern, central and southern Norway across four summers (2013–2016). Additionally, two museum-archived feathers from 1979 to 1989 were included. Stable carbon (δ13C) and nitrogen isotopes (δ15N) were used as dietary proxies. In total, 11 PFAS (sum range 8.25–215.90 ng g−1), 15 PCBs (4.19–430.01 ng g−1), 6 OCPs (1.48–220.94 ng g−1), 5 PBDEs (0.21–5.32 ng g−1) and 3 OPEs (4.49–222.21 ng g−1) were quantified. While we observed large variation in the values of both stable isotopes, suggesting a diverse diet of the eagle-owls, only δ13C seemed to explain variation in PFAS concentrations. Geographic area and year were influential factors for δ15N and δ13C. Considerable spatial variation was observed in PFAS levels, with the southern area showing higher levels compared to northern and central Norway. For the rest of OHCs, we observed between-year variations; sum concentrations of PCBs, OCPs, PBDEs and OPEs reached a maximum in 2015 and 2016. Concentrations from 1979 to 1989 were within the ranges observed between 2013 and 2016. Overall, our data indicate high levels of legacy and emerging OHCs in a top predator in Norway, further highlighting the risk posed by OHCs to wildlife

Effet de l’hydratation et du rapport E/C sur les paramètres de la rugosité de surface de pâtes cimentaires

National audienceCe travail s'inscrit dans le cadre du projet national à Fond Unique Interministériel, nommé ERGOFORM (ERGOnomic FORMwork-Système de coffrage auto-stable diminuant la pénibilité de chantier), qui vise à mettre au point un procédé de coffrage innovant. Quatre pâtes de ciment ont été élaborées avec des rapports Eau sur Ciment (E/C) de respectivement 0,30, 0,35, 0,40 et 0,45. L'évolution des propriétés physiques et mécaniques des pâtes de ciment ont été mesurées : la porosité accessible à l'eau sous vide, les résistances à la compression et en flexion trois points. L'évolution des paramètres de rugosité en fonction du temps de cure a été analysée par microscopie interférométrique et microscopie électronique à balayage environnemental (MEB-E). Les résultats expérimentaux montrent que l'augmentation du dosage en ciment diminue la porosité accessible à l'eau et améliore les propriétés mécaniques à 24h (après décoffrage nommé T0). L'évolution de la porosité en fonction du temps de cure montre une augmentation se stabilisant après 4 jours d'immersion dans l'eau pour les pâtes cimentaires de rapports E/C de 0,40 et de 0,45 (Groupe 2). En revanche, cette augmentation se prolonge légèrement pour les pâtes de ciment 0,30 et 0,35 (Groupe 1). Par ailleurs, l'évolution des paramètres de rugosité est fonction du dosage en ciment. En effet, les analyses microscopiques et par diffraction des rayons X mettent en évidence une diminution de la quantité des pores en surface, mais aussi l'évolution des paramètres de rugosité par un changement de sa morphologie et la formation de portlandite même après 2 heures de cure normalisée. : The experimental study is part of the national project ERGOnomic FORMwork (Self-Stable Formwork System Reducing Site Difficulty) named ERGOFORM, which aims to develop an innovative formwork process for construction field. Four cement pastes were provided with different water-to-cement ratio (W/C), respectively, 0.30, 0.35, 0.40 and 0.45. The evolution of physical and mechanical properties of cement pastes was measured through water porosity under vacuum, compressive strength and flexural strength. The variation of the roughness parameters was performed by the interferometry microscope. The environmental scanning electron microscopy (E-SEM) was used to analyze the evolution of the surface morphology. The experimental results show that the increase of cement quantity decreases the water porosity and improves the mechanical properties of studied mix designs at 24 hours (after stripping, called T0). The evolution of porosity versus curing time shows that the variation stabilizes after 4 days of immersion in water for the ratio W/C 0.40 and 0.45, named G2 (Group 2). On the other hand, this variation slightly continued for cement pastes 0.30 and 0.35, named G1 (Group 1). Moreover, the evolution of roughness parameters is dependent on cement quantity in mix design. Indeed, the MEB coupling EDX and X-ray diffraction analyzes reveal a decrease in the amount of surface pores, but also the evolution of the roughness parameters by a change in its morphology and the formation of portlandite even after 2 hours of standardized cure