Effects of Physical and Visual Access to Prey on Patch Selection and Food Search Effort in a Sit-and-Wait Predator, the Black Phoebe

Abstract

Abstract. For sit-and-wait predators, a key factor influencing foraging decisions is the ability to detect and track prey, which is expected to vary with the physical and light properties of the environment. We assessed how changes in visual and physical prey availability altered perch selection and visual search activity (head-movement rate and bout length) in the Black Phoebe (Sayornis nigricans), a sit-and-wait flycatcher. We used an observational approach by studying individuals in foraging areas that varied in the ecological factors of interest across an urbanized landscape. Black Phoebes selected perches with high levels of tree and grass cover and low light intensity, which could increase access to prey and reduce predation risk. Visual searching for prey decreased as grass cover increased and tree cover decreased, likely because of less physical and visual obstruction. Visual searching increased with light intensity, probably as a result of the effects of glare, but chromatic contrast did not exer...