Drone Surveys Do Not Increase Colony-wide Flight Behaviour at Waterbird Nesting Sites, But Sensitivity Varies Among Species

Abstract

Aerial surveys can also disturb nesting colonial waterbirds, sometimes causing severe panic responses, nest abandonment, and delayed return times to the nest 13-15. It is common for birds to look up, scan more, or remain vigilant during aircraft overflights 16. Furthermore, prolonged vigilance can divert time and energy away from activities that are needed to increase individual fitness 17,18. However, some mixed-species nesting colonies are not significantly affected by aerial surveys, behaviourally or reproductively 19,20. Certain species, e.g., Least Tern (Sternula antillarum), Common Tern (Sterna hirundo), Gull-billed Tern (Gelochelidon nilotica), and Black Skimmer (Rynchops niger), do not react noticeably to manned aircraft, suggesting that overflights do not detract from their incubation behaviour 21. This is not always the case, as Adélie Penguins (Pygoscelis adeliae) are more prone to abandon nests after helicopter and fixed-wing aircraft surveys 15. Unmanned aerial vehicles (UAVs) have recently garnered attention for surveying wildlife. They have been used to survey a variety of avifauna, including Common Terns 22 , Black-headed Gulls (Chroicocephalus ridibundus) 23 , cliff-nesting seabirds 24 , and other species that lend themselves well to aerial photography. UAVs provide benefits that make them appealing for surveying wildlife, such as suitability for fine spatial resolution, researcher safety, transportability, cost, and the ability to easily switch out sensors or payloads 25. Perhaps the most important potential benefit UAVs provide is a small and quiet platform, which could potentially be less disturbing to wildlife than manned aircraft. Recent studies have found that some species of waterbirds are not significantly disturbed by UAV surveys when flown in horizontal transects 22,26-28. However, for Adélie and Gentoo Penguins (Pygoscelis papua), lower survey altitudes can exacerbate disturbance behaviour even when the UAV is flown horizontally 29. Due to the recent popularity and availability of UAVs among researchers, managers, and recreationists, there is a need to continue studying their effects on waterbirds. Knowledge gaps remain, especially regarding methodological best practices and operating thresholds in wildlife research and management. Although recent research has addressed disturbance caused by approach angle 24,26 , hovering 24,30 , and low altitude flyovers 30,31 , few studies have taken into consideration the impact of UAV surveys intended for obtaining high-resolution mosaicked orthophotos of large nesting sites. This type of survey is generally flown in horizontal strip transects and at reasonable heights, which enable photogrammetric ease and image stitching 32. For waterbirds in particular, few studies have investigated disturbance caused by horizontal UAV surveys at heights greater than 50 m 22,33 , even though it has been suggested that count accuracy does not significantly increase for imagery below 90 m 34. Safe operating thresholds are needed not only for wildlife researchers,...

Drones, Gulls and Urbanity: Interaction between New Technologies and Human Subsidized Species in Coastal Areas

“…Negative reactions to drones have been evaluated in several marine species of different taxa, which were present in a few species in marine environments. Most of these reactions were recorded in birds during the breeding season in species highly sensitive to disturbance and sometimes with an intense territorial behavior [16,18]. During breeding, other studies have suggested that breeders react to flying movements rather than sound disturbance [33].…”

“…Several reactions have been recorded in wildlife in response to drones; some species ignore the presence of UAVs completely [16], and others react by evading [17] or confronting them, attacking the flying device in their territories aggressively [18]. Urban and semi-urban are the most utilized areas for UAVs because of the high density human population and connectivity facilities.…”

Breeding Ecology of Mottled Ducks: A Review

“…Ground‐based surveys, especially those in which an airboat is involved, would likely encourage broods to seek refuge in nearby escape cover, therefore hindering the survey. Unmanned aerial vehicles have been used to survey broods across a variety of landscapes (Pöysä et al 2018) and cause little disturbance to breeding birds (Barr et al 2020). Additionally, unmanned aerial vehicles equipped with thermal‐imaging cameras allow researchers to identify the presence of broods even when in dense vegetative cover.…”

Nesting Common Eiders (Somateria mollissima) show little behavioral response to fixed-wing drone surveys

“…However, this is an area of growing research. Several studies have anecdotally evaluated behavior, but it has not been until recent years that controlled studies focused on behavior have been conducted (Barnas et al 2018b;Barr et al 2020;Egan et al 2020). A review of behavioral studies by Mulero-Pázmány et al (2017) concluded that there are many factors that impact behavioral responses of wildlife which include species, life history characteristics, drone platform characteristics, altitude, and flight approaches (at angles vs. directly at animals).…”