Nightjars, rabbits, and foxes interact on unpaved roads: spatial use of a secondary prey in a shared‐predator system

Abstract

Citation: Camacho, C., P. Saez-Gomez, J. Potti, and J. M. Fedriani. 2017. Nightjars, rabbits, and foxes interact on unpaved roads: spatial use of a secondary prey in a shared-predator system. Ecosphere 8(1):e01611. 10.1002/ecs2.1611Abstract. Linear developments, such as roads and firebreaks, can increase encounter rates between predator and prey, which could affect predator-prey interactions and community dynamics. However, the extent to which prey responses at the interface between natural and anthropogenic habitats may be compared to those at the interface between natural habitats is unclear. Here, we used a shared-predator system to investigate the spatial response of red-necked nightjars (Caprimulgus ruficollis) to changing predation risk on roads, measured as the abundance of red foxes (Vulpes vulpes), and their primary prey (rabbits, Oryctolagus cuniculus). Because all three species coexist closely on unpaved roads in Doñana National Park (Spain), we predicted that nightjars would experience increased predation risk during periods of high fox and low rabbit abundances. Birds could then modify their space use at a broad scale by moving away from risky unpaved roads or, at a finer scale, by seeking foraging microsites facilitating escape from attacks. Between 2011 and 2012, mean rabbit abundance on roads increased by 50%, and fox abundance decreased by 80%, indicating a substantial decrease in predation risk for nightjars. Unexpectedly, nightjar occurrence on roads did not increase as a consequence of the decrease in fox predation risk. However, nightjars foraging on roads became less apprehensive in their use of linear strips of roadside cover, which is known to function as a physical barrier against fox attacks. Specifically, under high predation risk, most nightjars perched on the ground nearby (<15 cm) tall (>150 cm) vegetation, whereas when predation risk decreased, they shifted to more exposed microsites near shorter (<1 m) stands, but rarely close to cover (>45 cm). Nightjars' preference for areas of high predator abundance strongly suggests that flexible microhabitat selection allows them to manage the overall predation risk independently of predator abundance. Our results highlight the importance of linear developments in determining risk exposure and prey use of apparently dangerous habitats and thus may contribute to a better understanding of risky behaviors of prey.

Implications of shared predation for space use in two sympatric leporids

“…Few field studies on terrestrial systems have quantitatively investigated the effects of shared predation on fine‐scale space use by prey species (Camacho et al, ; Johnson et al, ; Oliver et al, ). As expected, the presence of rabbits (i.e., introducing shared predation) affected the predator–prey space race for hares more strongly than vice versa.…”

“…However, the implications of shared predation on prey space use remain poorly studied (Chaneton & Bonsall, 2000). In particular, more insight is needed on the fine-scale space use by prey and predator species as a result of the interaction between habitat riskiness and the presence or absence of shared predation (see e.g., Camacho, Sáez-Gómez, Potti, & Fedriani, 2017). Spatial variation in habitat riskiness, for example, can prevent depensatory predation and extinction of prey (Sinclair et al, 1998).…”

Environmental factors influencing road use in a nocturnal insectivorous bird

“…For instance, predation risk could influence the spatial decisions of foraging nightjars (Lima and Dill 1990;Lima 1998). However, the risk of predation on the surveyed roads rarely changes at time scales as short as a few days or weeks (Camacho et al 2017). Fluctuations in the availability of both flying insects (e.g.…”

“…Many aspects of the movement ecology and habitat selection of nightjars have been studied in the study area over the past decade (e.g. Camacho 2013a, b;Camacho et al 2014Camacho et al , 2017. Because this study focuses on nightjar use roads, the sampling area consisted of a 24-km 6 network of paved (7 km) and gravel (17 km) roads crossing a mosaic landscape of sparse Mediterranean shrublands, cattle-grazed grasslands, and pine tree plantations (see Camacho et al 2014 for a detailed description of the study site).…”

Nightjars may adjust breeding phenology to compensate for mismatches between moths and moonlight

“…We suspect that this level of defense could allow at least one chick to escape detection by a variety of predators. Differences in chick survival between years and lowest survival in the middle of the season could also be related to local differences in predator activity and availability of alternative prey (Camacho, Sáez‐Gómez, Potti, & Fedriani, ). For example, turtle nests (possibly Chelydra serpentine , Chrysemys picta , and Graptemys geographica ) are abundant at our study site (personal observation), which could attract predators like raccoons.…”