Coping with fast climate change in northern ecosystems: mechanisms underlying the population‐level response of a specialist avian predator

Abstract

Northern ecosystems are facing unprecedented climate modifications, which pose a major threat for arctic species, especially the specialist predator guild. However, the mechanisms underlying responses of predators to climate change remain poorly understood. Climate can influence fitness parameters of predators either through reduced reproduction or survival following adverse weather conditions, or via changes in the population dynamics of their main prey. Here, we combined three overlapping long‐term datasets on the breeding density and parameters of a rodent‐specialist predator, the rough‐legged buzzard Buteo lagopus, its main prey population dynamics and climate variables, collected in subarctic areas of Finland and Norway, to assess the impact of changing climate on the predator reproductive response. Rough‐legged buzzards responded to ongoing climate change by advancing their laying date (0.1 d yr−1 over the 21 yr of the study period), as a consequence of earlier snowmelt. However, we documented for the same period a decrease in breeding success, which principally resulted from an indirect effect of changes in the dynamics of their main prey, i.e. grey‐sided voles Microtus oeconomus, and not from the expected negative effect of unfavorable weather conditions during the brood‐rearing period on nestling survival. Additionally, we showed the striking impact of autumn and winter weather conditions on vole population growth rates in subarctic ecosystems, with a strong positive correlation between mean snow depth in autumn and winter and both winter and summer population growth rates. Our results highlighted that, in northern ecosystems, ongoing climate change has the potential to impact specialist predator species through two mechanistic linkages, which may in the long‐run, threaten the viability of their populations, and lead to potential severe cascading trophic effects at the ecosystem level.

Transferability of biotic interactions: Temporal consistency of arctic plant–rodent relationships is poor

“…Vegetation composition within both habitats exhibits profound spatial variation in the study area and ranges from dominance of palatable plants to dominance of nonpalatable plants (Ravolainen, Bråthen, Ims, Yoccoz, & Soininen, ; Soininen, Ravolainen, et al., ). Rodent populations in the region normally exhibit a synchronous 4‐ to 5‐year cycle (Figure ., Terraube et al., ). The tritrophic food web of the region is described in detail in Ims, Jepsen, Stien, and Yoccoz (), and summary statistics describing various abiotic (e.g., temperature and precipitation) and biotic (e.g., main predators and other herbivores) factors are given in Supporting Information Appendix S1; Table .…”

Flexibility in a changing arctic food web: Can rough‐legged buzzards cope with changing small rodent communities?

“…The rough‐legged buzzard (hereafter buzzard) is a moderate small rodent specialist (Hellström, Nyström, & Angerbjörn, ; Mechnikova, ; Osmolovskaya, ; Therrien, Gauthier, Korpimäki, & Bêty, ). In areas with small rodent cycles, the number of breeding pairs and the breeding success vary greatly from year to year following prey densities (Sundell et al, ; Terraube et al, ; Therrien et al, ). It has been suggested that buzzards are nomadic raptors, searching over large areas for favorable conditions with high abundance of small rodents (Sundell et al, ; Tast, Kaikusalo, & Lagerström, ).…”

“…Buzzards prey both on lemmings and voles, and can breed relying exclusively on lemmings (Beardsell et al, ) or exclusively on voles (Terraube et al, ). However, Hellström et al () showed that in northern Sweden, the functional response of buzzards to Norwegian lemmings ( Lemmus lemmus ) was steeper than the response to grey‐sided voles ( Myodes rufocanus ), reflecting a clear preference for lemmings.…”

Climate variability and the timing of spring raptor migration in eastern North America

“…Certain life history attributes appear to constrain climatic responsiveness, which may lead to asynchrony in phenological events across trophic levels and cause population declines (Visser et al , Both et al , Møller et al , Terraube et al ). Mismatches between reproductive timing and food availability are expected to become more severe with increasing trophic level (Both et al , Visser et al ), as for example, from granivorous sparrows to carnivorous hawks.…”