Low‐budget ready‐to‐fly unmanned aerial vehicles: an effective tool for evaluating the nesting status of canopy‐breeding bird species

Remotely controlled, unmanned aerial vehicles (UAVs) promise to be of high potential for a variety of applications in ecological and behavioural research. Off‐the‐shelf solutions have recently become available for civil use at steeply decreasing costs. In this study, we explored the utility of an UAV equipped with an on‐board camera (14 megapixel photo and 1920 × 1080 pixel video resolution) in assessing the breeding status, offspring number and age of a canopy‐breeding bird species, the hooded crow Corvus corone cornix . We further quantified performance and potential time savings using the UAV versus inspection with alternative approaches (optical instruments, camera on a telescopic rod, tree climbing). Nesting status, number and approximate age of nestlings could be assessed with good success in all 24 attempts using the UAV. Eighty‐five percent of the time required for inspection by climbing could be saved. Disturbance was moderate and lower than caused by climbing or using a camera on a telescopic rod. Additionally, UAV usage avoided tree damage and circumvented health risks associated with tree‐climbing.