'Bodyguard' plants: Predator-escape performance influences microhabitat choice by nightjars

摘要

Prey are typically assumed to avoid their predators. However, habitat selection patterns of prey might depend upon their ability to use particular landscape elements to manage their escape options from predator encounters. During two breeding seasons, I studied habitat use and behaviour of red-necked nightjars (Caprimulgus ruflcollis) foraging under the risk of predation by red foxes (Vulpes vulpes) in southwestern Spain. Nightjars exhibited nearly invariable foraging site choice and body positioning behaviour based on the architecture of vegetation near foraging sites. Nightjars actively chose to sit <50cm from >120 cm-tall shrubs or trees while facing away from vegetation cover. Vegetation behind nightjars significantly increased their aerial escape opportunities from terrestrial attacks during their peak activity period, when nightjars reveal visible feather bands during their foraging sallies from the ground and their cryptic colouration may not always match the background. Spatial overlap of nightjars and foxes along roads suggests that microhabitat selection by these birds may in part depend on the chance of escape from predator encounters rather than on the probability of encountering predators. I conclude that the interplay between high escape efficiency and visibility have probably contributed to the evolution of foraging site selection by caprimulgids using bare grounds and cattle, horse and camel trails as the natural counterpart of roads.