Nest predator avoidance during habitat selection of a songbird varies with mast peaks and troughs

Predation risk is vital in determining habitat quality. But landscapes of fear are complex and dynamic, such as temperate deciduous forests characterized by intermittent, synchronized production of large seed crops (mast peaks). These resource pulses elevate the magnitude of predation risk via direct or indirect effects, possibly altering also predator avoidance strategies of a prey. Yet, how animals manage predation risk via informed habitat selection and how this depends on ecological context remains poorly explored. We studied risk-sensitive settlement behavior of wood warbler Phylloscopus sibilatrix. We tested the hypothesis that warblers flexibly avoid predators (Eurasian jays Garrulus glandarius) during habitat selection but that their interactions are mediated by mast seeding, which is known to elevate the overall nest predation risk for warblers through its cascading effects on population dynamics of rodents and generalist predators. We used a playback experiment to manipulate warblers' perceived risk of nest predation by jays. We replicated the experiment in two consecutive years, followed by high or low seed crop. In the spring following mast trough, risky jay plots featured low abundance, late settlement, and poor pairing success compared to other treatments. In contrast, no response differences were found in the spring following mast seeding. Our results suggest that the way wood warblers adjust habitat choices to jay predation risk is indirectly mediated by mast seeding. This highlights plasticity in predator avoidance during prey habitat selection in complex and dynamic landscapes of fear, and the potential effects of mast seeding on animal behavior via indirect interactions.Significance statementAvoiding places with high nest predation risk during settlement decisions is believed to be widespread in birds. However, the mechanistic understanding of how birds acquire and use information about ambient nest predation risk to fine-tune settlement decisions is still limited. Using a playback experiment, we show that wood warblers eavesdrop on predator calls and avoid settling at sites with high perceived risk of nest predation by Eurasian jays. However, the way warblers adjust habitat choices to the nest predation risk posed by jays appears to be affected by tree mast seeding. This is potentially due to cascading effects of masting on the population dynamics of rodents and generalist predators, creating temporal peaks of elevated nest predation risk for wood warblers. Our study highlights plasticity in predator avoidance during prey settlement behavior in temporally variable, pulsed-resources ecosystems.