Linking geomorphological processes and wildlife microhabitat selection: nesting birds select refuges generated by permafrost degradation in the Arctic

Abstract

To gain better insight into the cascading impact of warming-induced changes in the physical landscape on biodiversity, it is crucial to better understand links between abiotic and ecological processes governing species distribution. Abiotic processes shaping the physical characteristics of the environment could significantly influence predator movements in the landscape and ultimately affect biodiversity through interspecific interactions. In the Arctic tundra, the main terrestrial predator (Arctic fox) avoids patches of wetlands composed of ponds with islets that can act as refuges for prey. Little is known about the geomorphological processes generating islets selected by prey species. Our study aimed to identify (i) the physical characteristics of islets selected by Arctic-nesting birds and (ii) the geomorphological processes generating islets available in the landscape. Over two breeding seasons, we determined the occurrence of nesting birds (cackling goose, glaucous gull, and red-throated loon) on islets (N = 396) found over a 165 km2 area on Bylot Island (Nunavut, Canada). Occupied islets were located further away from the shore (10.6 m ± 7.3 SD vs. 7.4 m ± 6.8 SD) and surrounded by deeper water (33.6 cm ± 10.6 SD vs. 28.1 cm ± 11.5 SD) than unoccupied islets. As expected, all three bird species selected islets less accessible to Arctic foxes, with nesting occurrence increasing with distance to shore and water depth around islets. Based on high-resolution satellite imagery and field observations, we found that ice-wedge polygon degradation generated the majority of islets (71 %) found in the landscape. Those islets were on average farther from the shore and surrounded by deeper water than those generated by other processes. As polygon degradation is projected to accelerate in response to warming, new refuges will likely emerge in the Arctic landscape, but current refuges could also disappear. Changes in the rate of polygon degradation may thus affect Arctic tundra biodiversity by altering predator–prey interactions.