Predation Risk Does Not Delay Breeding but Reduces Nest Survival in High-Arctic Shorebirds

Understanding predator-prey interactions is crucial for correctly answering many fundamental research questions, given their behavioural, ecological and evolutionary consequences. Such interactions can result in the direct consumption of the prey, but also in behavioural responses such as changes in breeding phenology. Space use of predators and the associated predation risk is a dynamic process, resulting in constant adjustments by the prey at different spatiotemporal scales. In the Arctic, predator-prey interactions are expected to change owing to the ongoing climate change and the associated shifts in ecosystem composition. However, most studies investigating the impact of predation on ground-nesting birds use data from artificial nests that lack the behavioural component of incubation. Consequently, studies investigating the impact of predation risk on real nests are needed, especially in arctic ecosystems of relatively low productivity. Using nest data collected over 3 years in Northeast Greenland, we investigated how spatial variations in predation risk by arctic foxes (Vulpes lagopus) impacted daily nest survival rates and start of incubation dates of two sympatric species of sandpipers: the sanderling (Calidris alba) and the dunlin (Calidris alpina arctica). Fox spatial activity was estimated by calculating their Autocorrelated kernel Utilisation Distributions based on fine-scale GPS data. We found that both sandpiper species had higher daily nest survival rates in areas of low fox activity. However, sandpipers initiated their nests earlier in areas of high fox activity. Together, these results show that predation risk does not delay the breeding phenology of high-Arctic sandpipers, and that predation risk clearly translates into lower nest survival, as often claimed by previous studies using artificial nests.