Department of Natural Environmental Studies, Graduate School of Frontier Sciences, University of Tokyo, Tokyo, Japan.
Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo, Japan.
PLoS One. 2021 Jul 16;16(7):e0254454. doi: 10.1371/journal.pone.0254454. eCollection 2021.
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.
海鸟行为的研究主要依赖于动物携带的标签来收集信息，需要进行解释才能估计海上行为。由于从生物记录设备中识别浅潜水的难度，浅潜水鸟类觅食的细节比深潜水物种了解得更少。较小的视频记录仪的开发允许直接观察这些鸟类的行为，但代价是电池容量较短。然而，将视频记录仪与相对低功耗的加速度计相结合，可以开发出一种可靠的觅食检测方法。2018 年繁殖季节，在船桥大岛（39°24'N，141°59'E）将组合式视频和加速度记录仪附着在条纹剪水鹱上。视频记录被分类为行为类别（休息、过渡和觅食），并从加速度信号中生成检测方法。通过视频记录报告了两种觅食行为，即水面捕食和觅食潜水。水面捕食由连续的起飞和着陆组成（平均持续时间分别为 0.6 和 1.5 秒），而觅食潜水则是从空气和水面进行的浅层次表面潜水（平均持续时间为 3.2 秒）。鸟类在靠近海豚和大鱼等海洋捕食者的地方觅食。行为检测方法的结果与视频记录进行了验证，飞行、水面捕食和觅食潜水的平均真实和假阳性率分别为 90%和 0%、79%和 5%以及 66%和<1%。该检测方法适用于在 2018 年和 2019 年繁殖季节收集的更长时间的加速度和 GPS 数据集。觅食旅行持续 1-8 天，鸟类平均每天进行 16 次水面捕食和 43 次觅食潜水，占每日活动的<1%，而过渡和休息分别占 55%和 40%。这种觅食检测方法可以解决记录浅潜水觅食行为的困难，并为测量浅潜水海鸟物种的活动预算提供了一种手段。
