Predator activity, proactive anti-predator strategies, and nesting phenology produce a dynamic landscape of risk to tundra goose reproduction

Sean M Johnson-Bice , Chloé Warret Rodrigues, Holly E.L. Gamblin, Frank B. Baldwin, James D. Roth

Birds generally rely on proactive anti-predator strategies when selecting nest sites, as they have limited options to adapt to changing levels of risk once incubation begins. Arctic waterfowl often nest colonially as an anti-predator strategy but dispersed-breeding species may use other proactive strategies, such as nesting in areas perceived to be safer. However, empirical links between spatial patterns of predation risk and nest habitat selection or success are needed to better understand how predator activity shapes Arctic waterfowl reproduction. Using activity data from the main cursorial nest predators, Arctic and red foxes (Vulpes lagopus, V. vulpes), and aerial predators, we evaluate the influence predator activity has on Canada goose (Branta canadensis interior) nest habitat selection and success, and how nesting phenology mediates these effects. We compared habitat selection models fit to i) goose nest locations and ii) fox locations obtained from GPS collars and found that geese and foxes display nearly opposite patterns of selection for the same landscape traits. Geese selected sites that minimized their probability of encountering foxes while also maximizing their ability to detect foxes. Spatial predictions of fox activity revealed nests located in areas with higher probability of fox use had lower nest success, indicating fox space-use patterns reflect predation risk. Landscape heterogeneity influenced both fox and goose nest habitat selection patterns and, consequently, spatial variation in predation risk and reproductive success. Aerial predators appeared to have a lesser effect on spatial patterns of goose nest habitat selection and success. Spatial patterns of nest success were, however, strongly influenced by nesting phenology. Nests initiated earlier had a greater probability of successfully hatching, but these patterns depended on location; the benefits of nesting early decreased in areas of high fox activity. Our study demonstrates the mechanisms by which nesting phenology, predator activity, and landscape heterogeneity interact to shape bird reproduction, and provides an empirical demonstration of how our understanding of predation risk is enhanced by integrating both spatial and temporal dynamics.