Using drones to measure the status of cavity-nesting raptors

Many wildlife species, including hole-nesting raptors, occupy cavities that are challenging or unsafe for observers to examine. We conducted field tests using an inexpensive, off-the-shelf camera attached to an affordable commercial drone to assess the reproductive success of American kestrels (Falco sparverius), a small, cavity-nesting raptor. Specifically, we developed a system that consisted of (1) a wireless mini camera transmitting images to an observer’s phone and (2) a Mini-Mavic 2 drone controlled through direct line-of-sight piloting. Following successful preliminary flights involving chicken eggs and other inanimate objects, we field-tested the system in two kestrel nest boxes in the wild. The system accurately recorded the contents of all nest boxes during the trials, provided the wind speed remained below approximately 2.5 m/s (5 knots). However, wind speeds at this level were observed only 40% of the days in our study area during kestrel breeding, which limited the surveying opportunities. Our system offers a promising method for surveying wildlife inhabiting inaccessible cavities.