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

Paul G Mcdonald,Graham P Hall,John F Mcevoy

doi:10.7717/peerj.1831

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.

Highlights

Sourced data is critical to the understanding and census of many ecological systems, such as the use of remotely sensed satellite imagery to investigate the impacts of climate change or the movement ecology of nomadic species (Bartlam-Brooks et al, 2013; Blanco et al, 2008; Felix, 2000; Mueller et al, 2011; Roshier & Rumbachs, 2004) or estimating population sizes using aerial photography (Bako, Tolnai & Takacs, 2014; Trathan, 2004)
With the increasing popularity of unmanned aerial vehicles (UAVs) for ecological research in the past year, there has been a sharp increase in papers assessing the potential for disturbance of wild animals by UAVs (Ditmer et al, 2015; Dulava, Bean & Richmond, 2015; Pomeroy, O’Connor & Davies, 2015; Vas et al, 2015; Weissensteiner, Poelstra & Wolf, 2015)
Waterfowl are known to be sensitive to disturbance with relatively high values of flight initiation distance (FID) compared to other species (Bregnballe et al, 2009; Korschgen & Dahlgren, 1992; Madsen, 1995; Weston et al, 2012)

Summary

Introduction

Sourced data is critical to the understanding and census of many ecological systems, such as the use of remotely sensed satellite imagery to investigate the impacts of climate change or the movement ecology of nomadic species (Bartlam-Brooks et al, 2013; Blanco et al, 2008; Felix, 2000; Mueller et al, 2011; Roshier & Rumbachs, 2004) or estimating population sizes using aerial photography (Bako, Tolnai & Takacs, 2014; Trathan, 2004). Research targeting waterfowl populations is no exception. In this field, conservation and management policies concerning agricultural mitigation interventions or harvest seasons. Most waterfowl surveys of large water bodies are undertaken using fixed wing aircraft carrying trained observers (Kingsford, 1999; Petrie, Shannon & Wilcox, 2002). Satellite imagery is often sufficient for larger taxa, such as several mammal species on the African savannah (Yang et al, 2014) but is considered unsuitable for smaller taxa such as waterfowl (Conant, Groves & Moser, 2007)

Methods

Results

Conclusion