A circumpolar study unveils a positive non-linear effect oftemperature on arctic arthropod availability that may reduce therisk of warming-induced trophic mismatch for breeding shorebirds

Seasonally abundant arthropods are a crucial food source for many migratorybirds that breed in the Arctic. In cold environments, the growth and emergence ofarthropods are particularly tied to temperature. Thus, the phenology of arthropodsis anticipated to undergo a rapid change in response to a warming climate, potentiallyleading to a trophic mismatch between migratory insectivorous birds and their prey.Using data from 19 sites spanning a wide temperature gradient from the Subarcticto the High Arctic, we investigated the effects of temperature on the phenology andbiomass of arthropods available to shorebirds during their short breeding seasonat high latitudes. We hypothesized that prolonged exposure to warmer summertemperatures would generate earlier peaks in arthropod biomass, as well as higherpeak and seasonal biomass. Across the temperature gradient encompassed by ourstudy sites (>10°C in average summer temperatures), we found a 3-day shift inaverage peak date for every increment of 80 cumulative thawing degree-days.Interestingly, we found a linear relationship between temperature and arthropodbiomass only below temperature thresholds. Higher temperatures were associatedwith higher peak and seasonal biomass below 106 and 177 cumulative thawingdegree-days, respectively, between June 5 and July 15. Beyond these thresholds,no relationship was observed between temperature and arthropod biomass. Ourresults suggest that prolonged exposure to elevated temperatures can positivelyinfluence prey availability for some arctic birds. This positive effect could, in part,stem from changes in arthropod assemblages and may reduce the risk of trophicmismatch. Sarctic arthropods, arctic breeding shorebirds, climate warming, insectivorous birds,invertebrate biomass, phenology, trophic mismatcpublishedVersio

Étude à large échelle spatiale pour évaluer l'effet de la température sur la disponibilité des arthropodes pour les oiseaux insectivores en Arctique

RÉSUMÉ: Les arthropodes arctiques sont une ressource essentielle à la reproduction des oiseaux insectivores nichant en Arctique. Cependant, le réchauffement climatique en cours est susceptible d'avoir un effet sur la disponibilité des arthropodes pour les oiseaux, notamment en affectant leur phénologie. Dans le but de mieux évaluer la possibilité d'une désynchronisation trophique entre les oiseaux et leurs proies, nous avons examiné l'effet de la température sur la disponibilité des arthropodes pour les oiseaux de l'Arctique. À l'aide de données provenant de 19 sites d'étude distribués le long d'un large gradient de température (du Subarctique à l'extrême Haut Arctique), nous avons examiné comment la température est reliée à la phénologie et à la biomasse d'arthropodes disponible pour les oiseaux durant leur saison de reproduction. Nos prédictions étaient que des températures plus élevées seraient associées à des dates de pic de biomasse d'arthropodes plus hâtives et à des biomasses maximales et saisonnières plus élevées. Tel qu'attendu, nos résultats montrent que la date du pic de biomasse est devancée quand la température estivale est plus élevée. Cet effet n'est cependant pas très marqué, avec un pic d'arthropodes devancé de 4 jours pour une augmentation de température estivale de 80 degrés-jours (soit environ 2°C d'augmentation de la température moyenne estivale). Nos résultats montrent aussi que la relation entre la température et la biomasse (maximale et saisonnière) n'est pas linéaire. En effet, les températures plus élevées sont associées à des biomasses d'arthropodes plus élevées, mais seulement en-dessous d'un certain seuil de température estivale (<114-177 degrés-jours). Au-delà de ce seuil, nous n'avons observé aucune relation entre la température et la biomasse d'arthropodes disponible. En se basant sur l'approche de substitution du temps par l'espace, et en considérant les effets combinés de la température sur la phénologie et la biomasse des arthropodes, notre étude suggère que les risques de désynchronisation trophique causée par le réchauffement pourraient être moindres que suggérées par des études antérieures, pour les oiseaux du Haut Arctique qui se nourrissent d'une grande diversité d'arthropodes. -- Mot(s) clé(s) en français : disponibilité des arthropodes, oiseaux insectivores, changements climatiques, collaboration pan-Arctique. -- ABSTRACT: Arctic arthropods are an essential resource for the reproduction of insectivorous birds nesting in the Arctic. However, current climate warming is likely to have an effect on arthropod availability for birds by affecting their phenology. In order to better evaluate the possibility of a trophic mismatch between birds and their prey, we investigated the effect of temperature on arthropod availability for arctic birds. Using data from 19 study sites distributed along a large temperature gradient (from the Subarctic to the extreme High Arctic), we investigated the effect of temperature variation on arthropod phenology and biomass available to birds during their breeding season. Our predictions were that higher temperatures would be associated with an earlier peak arthropod biomass, as well as a higher peak biomass and seasonal biomass of arthropods. As expected, our results show that the date of peak biomass advances when summer temperature is higher. However, this effect is relatively weak across our temperature gradient, with a 4-day shift in peak arthropod biomass date for an increase of 80 degree days (roughly equivalent to 2°C in average summer temperature). Our results also show that the relationship between temperature and arthropod biomass is not linear. Indeed, higher temperatures are associated to higher peak arthropod biomass values, but only under a temperature threshold (<114-177 degree-days). Above this threshold, no relationship was observed between temperature and arthropod biomass. Based on a space for time approach, and considering the combined effects of temperature on arthropod phenology and biomass, our study suggests that the risk of trophic mismatch caused by warming could be lower than what previous studies suggest for High Arctic birds feeding on a wide diversity of arthropods. -- Mot(s) clé(s) en anglais : arthropod availability, insectivorous birds, climate change, pan-Arctic collaboration