WATLAS: high-throughput and real-time tracking of many small birds in the Dutch Wadden Sea

Abstract

Tracking animal movement is important for understanding how animals interact with their (changing) environment, and crucial for predicting and explaining how animals are affected by anthropogenic activities. The Wadden Sea is a UNESCO World Heritage Site and a region of global importance for millions of shorebirds. Due to climate change and anthropogenic activity, understanding and predicting movement and space-use in areas like the Wadden Sea is increasingly important. Monitoring and predicting animal movement, however, requires high-resolution tracking of many individuals. While high-resolution tracking has been made possible through GPS, trade-offs between tag weight and battery life limit its use to larger species. Here, we introduce WATLAS (the Wadden Sea deployment of the ATLAS tracking system) capable of monitoring the movements of hundreds of (small) birds simultaneously in the Dutch Wadden Sea. WATLAS employs an array of receiver stations that can detect and localize small, low-cost tags at fine spatial (metres) and temporal resolution (seconds). From 2017 to 2021, we tracked red knots, sanderlings, bar-tailed godwits, and common terns. We use parts of these data to give four use-cases revealing its performance and demonstrating how WATLAS can be used to study numerous aspects of animal behaviour, such as, space-use (both intra- and inter-specific), among-individual variation, and social networks across levels of organization: from individuals, to species, to populations, and even communities. After describing the WATLAS system, we first illustrate space-use of red knots across the study area and how the tidal environment affects their movement. Secondly, we show large among-individual differences in distances travelled per day, and thirdly illustrate how high-throughput WATLAS data allows calculating a proximity-based social network. Finally, we demonstrate that using WATLAS to monitor multiple species can reveal differential space use. For example, despite sanderlings and red knots roosting together, they foraged in different areas of the mudflats. The high-resolution tracking data collected by WATLAS offers many possibilities for research into the drivers of bird movement in the Wadden Sea. WATLAS could provide a tool for impact assessment, and thus aid nature conservation and management of the globally important Wadden Sea ecosystem.

Red knots in Europe - a dead end host species or a new niche for highly pathogenic avian influenza?

“…Former studies have shown that red knots in the Wadden Sea are highly mobile and may switch between foraging sites and high tide roosts, respectively, in short periods of time (42, 43). In addition, virological investigations confirmed viral loads in oropharyngeal and cloacal samples suggesting virus shedding and transmission.…”

Environmental factors influencing red knot (Calidris canutus islandica) departure times of relocation flights within the non‐breeding period

“…We caught red knots using mist‐nets on the Griend and Richel mudflats in the Wadden Sea, the Netherlands (53°15′ N, 5°15′ E), between July and October in 2019 ( n = 251) and 2020 ( n = 244). We equipped them with lightweight ATLAS tags (4.4 g, ~3.4% of their body mass), which we tracked with a high‐resolution regional‐scale reverse‐GPS tracking system (Beardsworth et al., 2022 ; Bijleveld et al., 2022 ; Weiser et al., 2016 ). The Wadden Sea ATLAS (WATLAS) tracking area is approximately 1400 km 2 comprising a total of 26 receiver stations (Data S1 ) (Beardsworth et al., 2022 , Bijleveld et al., 2022 ).…”

“…We equipped them with lightweight ATLAS tags (4.4 g, ~3.4% of their body mass), which we tracked with a high‐resolution regional‐scale reverse‐GPS tracking system (Beardsworth et al., 2022 ; Bijleveld et al., 2022 ; Weiser et al., 2016 ). The Wadden Sea ATLAS (WATLAS) tracking area is approximately 1400 km 2 comprising a total of 26 receiver stations (Data S1 ) (Beardsworth et al., 2022 , Bijleveld et al., 2022 ). Tags emit a radio signal at 434 MHz and if at least three receiver stations detect the transmission, the system can calculate a location based on the transmission time of arrival.…”

“…Until recently, we lacked the technology to precisely track the timing of flight initiation of large numbers of individuals (Nathan et al., 2022 ). Here, we used a high‐resolution regional reverse‐GPS tracking system (ATLAS; Beardsworth et al., 2022 ; Bijleveld et al., 2022 ; Nathan et al., 2022 ) to identify departure times of red knots crossing the North Sea towards the British Isles. For those that departed on these relocation flights, we determined which conditions they selected for at their departure times and compared these to other available departure times.…”

Robust Time-of-Arrival Location Estimation Algorithms for Wildlife Tracking

“…ATLAS has proven to be a maintainable and productive regional high-throughput wildlife tracking system. It can track many species of wild animals at high temporal and spatial resolution using ToA radio transmitter localization [3,4,[12][13][14]. Six separate ATLAS systems, each consisting of 5 to 25 receivers, in four countries have tracked over 7000 transmitters, called tags, over the past 8 years, and a few more systems are under construction.…”