Evaluation of unmanned aerial vehicle shape, flight path and camera type for waterfowl surveys: disturbance effects and species recognition

Abstract

The use of unmanned aerial vehicles (UAVs) for ecological research has grown rapidly in recent years, but few studies have assessed the disturbance impacts of these tools on focal subjects, particularly when observing easily disturbed species such as waterfowl. In this study we assessed the level of disturbance that a range of UAV shapes and sizes had on free-living, non-breeding waterfowl surveyed in two sites in eastern Australia between March and May 2015, as well as the capability of airborne digital imaging systems to provide adequate resolution for unambiguous species identification of these taxa. We found little or no obvious disturbance effects on wild, mixed-species flocks of waterfowl when UAVs were flown at least 60m above the water level (fixed wing models) or 40m above individuals (multirotor models). Disturbance in the form of swimming away from the UAV through to leaving the water surface and flying away from the UAV was visible at lower altitudes and when fixed-wing UAVs either approached subjects directly or rapidly changed altitude and/or direction near animals. Using tangential approach flight paths that did not cause disturbance, commercially available onboard optical equipment was able to capture images of sufficient quality to identify waterfowl and even much smaller taxa such as swallows. Our results show that with proper planning of take-off and landing sites, flight paths and careful UAV model selection, UAVs can provide an excellent tool for accurately surveying wild waterfowl populations and provide archival data with fewer logistical issues than traditional methods such as manned aerial surveys.

Application of Low-Cost Fixed-Wing UAV for Inland Lakes Shoreline Investigation

“…Both have advantages and disadvantages which define their potential applications. Each UAV has a unique take-off and landing system (McEvoy et al 2016). The fixed-wing systems require a larger clear area for both take-off and landing.…”

“…The main limitations are price, legal constraints and the need to ensure the technical expertise of the pilot. As a result, the UAV use usually requires cooperation with commercial companies (McEvoy et al 2016). The application of the multi-rotor UAV in shoreline measurements is limited due to their range and working time.…”

Escape responses of terrestrial and aquatic birds to drones: Towards a code of practice to minimize disturbance

“…Higher altitudes than those tested would presumably eliminate responses (e.g. responses are absent above 40 m for non‐breeding waterfowl, McEvoy, Hall, & McDonald, ; 60 m for Crested Terns Thalasseus bergii , Bevan et al, ). Response rates at altitudes of 4 and 10 m remained high, thus even our higher altitude treatment was evidently perceived as a threat.…”

Can drones count gulls? Minimal disturbance and semiautomated image processing with an unmanned aerial vehicle for colony‐nesting seabirds

“…McEvoy et al. () determined that 40 m was a suitable height for flying a small UAV over nonbreeding wildfowl, with disturbance noted at flying heights below this, or whilst the UAV rapidly changed direction or altitude when above the birds. Hodgson et al.…”