Surveying cliff-nesting seabirds with unoccupied aircraft systems in the Gulf of Alaska

Abstract

Drones, or unoccupied aircraft systems (UAS), can transform the way scientific information on wildlife populations is collected. UAS surveys produce accurate estimates of ground-nesting seabirds and a variety of waterbirds, but few studies have examined the trade-offs of this methodology for counting cliff-nesting seabirds. In this study, we examined how different UAS survey parameters might influence seabird counts for population monitoring and assessed behavioral responses to aerial surveys for three sub-Arctic seabird taxa in the Gulf of Alaska: common murres (Uria aalge), black-legged kittiwakes (Rissa tridactyla), and pelagic and double-crested cormorants (Phalacrocorax pelagicus and Phalacrocorax auritus). We flew two commercially available models of UAS in planned approaches at different speeds and distances from colonies during incubation and chick-rearing periods. We compared counts from UAS-derived images with those from vessel-based photography and assessed video recordings of individual birds’ behaviors for evidence of disturbance during UAS operations and control phases. Count estimates from UAS images were similar to or higher than those from conventional vessel-based images, and UAS were particularly effective at photographing birds at sites with high cliff walls or complex topography. We observed no significant behavioral responses to the UAS by murres or cormorants, but we did observe flushing by black-legged kittiwakes during UAS flights; most of these birds were not incubating or brooding. At both the colony and individual level, we observed slightly greater responses to the smaller UAS platform and closer approaches. These results inform both species specific and general best practices for research and recreational usage of UAS near cliff-nesting seabird colonies.

Accurate abundance estimation of cliff-breeding Bounty Island shags using drone-based 2D and 3D photogrammetry

“…3D models effectively provide a post hoc tool and verification method for field-based surveys. Study sites can be revisited virtually and without the constraints of a fixed vantage point, which is a significant limitation, particularly in boat-based surveys (Bishop et al 2022). As our study shows, the commonly used top-down view of the study area can considerably underestimate occupation in steep cliffs and overhangs.…”

“…Our study is the first to use a combination of high-resolution orthomosaics and textured 3D models to count seabirds. The use of drone-based surveys has seen a marked increase in recent years (Hodgson et al 2018, Pfeifer et al 2019, Bishop et al 2022. The general approach to such drone surveys is to record sequences of top-down (nadir) photographs and subsequently generate composite, high-resolution images of the survey area either by stitching images (Mattern et al 2021, Dunn et al 2021, Parker and Rexer-Huber 2022 or using dedicated photogrammetry solutions (e.g., Oosthuizen et al 2020, Hayes et al 2021, Fudala and Bialik 2022.…”

The conservation impact of botanical drones: Documenting and collecting rare plants from vertical cliffs and other hard‐to‐reach areas

“…Scientists are now deploying uncrewed aircraft systems (UAS also called drones) to gather data from hard‐to‐reach areas including for DNA studies of whales from drone‐based respiratory blow samples (Atkinson et al., 2021), assessment of cliff‐dwelling seabird colonies (Bishop et al., 2022), and monitoring canopy infestations in palm trees (Kadethankar et al., 2021). Plants growing in hard‐to‐reach areas have also been studied using these emerging technologies including, for example, the study of water holding capacity of bromeliads in Brazil (Lehmann et al., 2022), systematic vertical transects to assess floristic abundance in China (Zhou et al., 2021), and in‐depth imaging and modelling of one specific cliff section in Italy (Strumia et al., 2020).…”