Video and acceleration records of streaked shearwaters allows detection of two foraging behaviours associated with large marine predators

Abstract

The study of seabird behaviour has largely relied on animal-borne tags to gather information, requiring interpretation to estimate at-sea behaviours. Details of shallow-diving birds’ foraging are less known than deep-diving species due to difficulty in identifying shallow dives from biologging devices. Development of smaller video loggers allow a direct view of these birds’ behaviours, at the cost of short battery capacity. However, recordings from video loggers combined with relatively low power usage accelerometers give a means to develop a reliable foraging detection method. Combined video and acceleration loggers were attached to streaked shearwaters in Funakoshi-Ohshima Island (39°24’N,141°59’E) during the breeding season in 2018. Video recordings were classified into behavioural categories (rest, transit, and foraging) and a detection method was generated from the acceleration signals. Two foraging behaviours, surface seizing and foraging dives, are reported with video recordings. Surface seizing was comprised of successive take-offs and landings (mean duration 0.6 and 1.5s, respectively), while foraging dives were shallow subsurface dives (3.2s mean duration) from the air and water surface. Birds were observed foraging close to marine predators, including dolphins and large fish. Results of the behaviour detection method were validated against video recordings, with mean true and false positive rates of 90% and 0%, 79% and 5%, and 66% and <1%, for flight, surface seizing, and foraging dives, respectively. The detection method was applied to longer duration acceleration and GPS datasets collected during the 2018 and 2019 breeding seasons. Foraging trips lasted between 1 − 8 days, with birds performing on average 16 surface seizing events and 43 foraging dives per day, comprising <1% of daily activity, while transit and rest took up 55 and 40%, respectively. This foraging detection method can address the difficulties of recording shallow-diving foraging behaviour and provides a means to measure activity budgets across shallow diving seabird species.

Automatic recording of rare behaviors of wild animals using video bio-loggers with on-board light-weight outlier detector

“…Recording videos of foraging is generally difficult because the frequency of foraging activities is quite low ( 28 ). Thus, the videos of foraging collected by our bio-loggers may contain novel behaviors related to foraging that we have not yet identified.…”

“…4 A). In general, shearwater species are well-known for floating on the water surface and dipping their head into the water before diving ( 28–31 ), which is often interpreted as a means of locating prey before submersion ( 29 , 30 ). Performing shallow dipping to confirm the location of fish schools before diving can reduce energy consumption and increase the probability of successful foraging.…”

Supervised versus unsupervised approaches to classification of accelerometry data

“…There is a growing trend in the classification literature calling for or using either supervised classification or post hoc calibration of behavior when conducting analysis of accelerometry or other biologging data (Elbroch et al, 2018 ; Garrod et al, 2021 ; Halsey, 2017 ; Halsey & Bryce, 2021 ; Rast et al, 2020 ; Van Walsum et al, 2020 ). The body of literature in this field is growing more robust as there is an increase in the diversity of species evaluated and analytical techniques considered.…”

“…There is a growing trend in the classification literature calling for or using either supervised classification or post hoc calibration of behavior when conducting analysis of accelerometry or other biologging data (Elbroch et al, 2018;Garrod et al, 2021;Halsey, 2017;Halsey & Bryce, 2021;Rast et al, 2020;Van Walsum et al, 2020).…”

Hidden rivals: the negative impacts of dolphinfish on seabird foraging behaviour

“…However, intense competition for shared prey species likely arises, influencing not only immediate foraging strategies but also annual distribution and interspecies dynamics [5]. Previous studies on the relationship between seabirds and underwater predators sharing prey have mainly focused on the instantaneous and local scales [1,2,[6][7][8][9]. Therefore, our understanding of the interspecific relationships among marine top predators at the air-sea boundary layer remains limited, especially at scales relevant to wide-ranging marine predators and their prey.…”