Field test of an automated radio-telemetry system: tracking local space use of aerial insectivores

Abstract

Documenting local space use of birds that move rapidly, but are too small to carry GPS tags, such as swallows and swifts, can be challenging. For these species, tracking methods such as manual radio‐telemetry and visual observation are either inadequate or labor‐ and time‐intensive. Another option is use of an automated telemetry system, but equipment for such systems can be costly when many receivers are used. Our objective, therefore, was to determine if an automated radio‐telemetry system, consisting of just two receivers, could provide an alternative to manual tracking for gathering data on local space use of six individuals of three species of aerial insectivores, including one Cliff Swallow (Petrochelidon pyrrhonota), one Eastern Phoebe (Sayornis phoebe), and four Barn Swallows (Hirundo rustica). We established automated radio‐telemetry systems at three sites near the city of Peterborough in eastern Ontario, Canada, from May to August 2015. We evaluated the location error of our two‐receiver system using data from moving and stationary test transmitters at known locations, and used telemetry data from the aerial insectivores as a test of the system's ability to track rapidly moving birds under field conditions. Median location error was ~250 m for automated telemetry test locations after filtering. More than 90% of estimated locations had large location errors and were removed from analysis, including all locations > 1 km from receiver stations. Our automated telemetry receivers recorded 17,634 detections of the six radio‐tagged birds. However, filtering removed an average of 89% of bird location estimates, leaving only the Cliff Swallow with enough locations for analysis of space use. Our results demonstrate that a minimal automated radio‐telemetry system can be used to assess local space use by small, highly mobile birds, but the resolution of the data collected using only two receiver stations was coarse and had a limited range. To improve both location accuracy and increase the percentage of usable location estimates collected, we suggest that, in future studies, investigators use receivers that simultaneously record signals detected by all antennas, and use of a minimum of three receiver stations with more antennas at each station.

Locating large insects using automated VHF radio telemetry with a multi‐antennae array

“…Alternatively, additional receiving stations could be installed to extend the detectable range of the system; for example, rather than deploying four receiving stations to create a 250 m 2 detection area, nine receiving stations would create a 500 m 2 detection area. Additional receiving stations, antennae on receiving stations and/or antennae with more elements could improve tracking insects in flight, as suggested by Lenske and Nocera (2018) for tracking birds. Using a transmitter with a greater pulse rate could also aid in tracking insects in flight (e.g.…”

“…Using a transmitter with a greater pulse rate could also aid in tracking insects in flight (e.g. see Lenske & Nocera, 2018) as well as decrease the error ellipse estimates.…”

“…Our ARTS utilized a model that incorporated both power–distance and power–angle relationships. Performance of the ARTS was evaluated using a low‐powered, 0.22 g transmitter, taking into account factors including height and orientation of the transmitter, vegetation between the transmitter and the receiving station, and rate and pattern of transmitter movement (see Crewe et al., 2019; Kays et al., 2011; Lenske & Nocera, 2018; Ward et al., 2013).…”

“…Automated radio telemetry systems (ARTS) have been proposed as a means to increase scalability, frequency in data collection intervals and potentially minimize errors in location estimates for insects (Kissling et al., 2014). Several research teams have described ARTS for tracking mammals and birds (Cochran et al., 1965, 2001; Crewe et al., 2019; Kays et al., 2011; Knight et al., 2019; Larkin et al., 1996; Lenske & Nocera, 2018; Motus Wildlife Tracking System, 2020; Ward et al., 2013). Most notably Kays et al.…”

Very small collars: an evaluation of telemetry location estimators for small mammals

“…Given the lag in GPS miniaturization, currently there are two primary methods of data collection from the micro-VHF trackers for small mammals: fixed, automated stations and manual triangulation via a simple, directional Yagi-Uda antenna and compass [14,19,27,28,30,33,34]. Unfortunately, while fixed, automated radio telemetry stations allow for increased data collection and reduce human interference with animal movements in the field, they are typically not viable in urban or highly suburban settings because of VHF signal interference in strength, directionality, and signal reflection or rebounding [35][36][37][38]. The remaining option is manual VHF telemetry.…”