Terrestrial arthropod abundance and phenology in the Canadian Arctic: modelling resource availability for Arctic-nesting insectivorous birds

Abstract

Arctic arthropods are essential prey for many vertebrates, including birds, but arthropod populations and phenology are susceptible to climate change. The objective of this research was to model the relationship between seasonal changes in arthropod abundance and weather variables using data from a collaborative pan-Canadian (Southampton, Herschel, Bylot, and Ellesmere Islands) study on terrestrial arthropods. Arthropods were captured with passive traps that provided a combined measure of abundance and activity (a proxy for arthropod availability to foraging birds). We found that 70% of the deviance in daily arthropod availability was explained by three temperature covariates: mean daily temperature, thaw degree-day, and thaw degree-day2. Models had an adjusted R2 of 0.29–0.95 with an average among sites and arthropod families of 0.67. This indicates a moderate to strong fit to the raw data. The models for arthropod families with synchronous emergence, such as Tipulidae (Diptera), had a better fit (average adjusted R2 of 0.80) than less synchronous taxa, such as Araneae (R2 = 0.60). Arthropod abundance was typically higher in wet than in mesic habitats. Our models will serve as tools for researchers who want to correlate insectivorous bird breeding data to arthropod availability in the Canadian Arctic.

Arctic-nesting birds find physiological relief in the face of trophic constraints

“…It is also important to note that these indices are based on current relationships between variables of climate and food availability at one study site in the low Arctic, therefore, the generality of these results will depend on whether these relationships hold across different habitats and future climate scenarios. Across a large geographical range in the Canadian Arctic where average summer temperatures varied by up to 6.8°C, relationships between climatic variables such as temperature, wind and rain, and arctic arthropod biomass have been shown to be relatively consistent25, providing some support for the generality of our results.…”

“…In our study the generation of independent indices using principal components analysis on the combined set of climate and food availability variables enabled us to account for multicollinearity between these variables and tease apart their respective effects with greater confidence. Although the principal components analysis does account for the problem of multicollinearity, due to the inextricable physiological link between the climate and arthropod biomass25, there is still some influence (loadings) of food variables within our index of climate. It is also important to note that these indices are based on current relationships between variables of climate and food availability at one study site in the low Arctic, therefore, the generality of these results will depend on whether these relationships hold across different habitats and future climate scenarios.…”

Interaction webs in arctic ecosystems: Determinants of arctic change?

“…Given the temporally extended peak of arthropod abundance in Zackenberg (Høye and Forchhammer 2008) compared with other arctic regions (Tulp and Schekkerman 2008; Bolduc et al 2013), current phenological mismatches will not necessarily result in negative fitness consequences for the avian predators. Effects may be limited, as long as arthropod prey abundance exceeds a minimal threshold for sufficient chick growth for a long time after the absolute annual peak in food abundance (Durant et al 2005).…”

Full Issue

“…), Rock Ptarmigan (Lagopus muta), sea ducks (Somateria spp. and Long-tailed Ducks [Clangula hyemalis]), freshwater fishes (Arctic char [Salvelinus alpinus]), and several terrestrial arthropod families (mostly Araneae, Muscideae, Chironomideae, Tipulideae, Carabideae, and Apideae; Bolduc et al 2013) represent other potential prey species present in the study site. Along the seashore, marine invertebrates in small pools and live or dead fishes could also constitute potential prey.…”