Mathilde Guglielmi
Projet
Refining the Use of Automated Radio Telemetry for Studying Bird MigrationToday, methods to track wildlife are increasingly accurate and user-friendly. One such method is an automated radio telemetry system (A.R.T.S.), which uses radio waves from a transmitter to detect the position and movement of an animal. An A.R.T.S consists of one or several automated radio receivers placed at one or several towers, which are equipped with arrays of directional antennas (Taylor et. al., 2017). The antennas are there to detect the signals coming from radio-tagged animals within their range. An A.R.T.S. is particularly helpful for tracking smaller organisms such as bats, birds, insects and other animals too small for satellite tags. The MOTUS system is an example of automated radio telemetry. It is a “continental-scaled network” (Taylor et al., 2017), in which researchers from across North America collaborate, as well as share data from their independently-run arrays in a common database. In the MOTUS A.R.T.S., all the tags are on the same frequency, which makes the system even more user-friendly. A MOTUS receiver consists of a receiver, such as a sensorgnome, which includes a box that captures signals and processes the signals using open software. Another option for the receiver is LOREX SRX/DX series, which has a very accurate global position system (Taylor et al. 2017). The sensorgnome syncs radio signals simultaneously, while the LOREX switches between signals in a sequential manner (Taylor et al., 2017). Limitations of MOTUS include: dead zones (on the ground), human-made structures, cell phone use, which interferes with signal detection especially at the time of day when many people connect, and the orientation of antennas (Taylor et al. 2017[K4]). The signals are processed at the Bird Studies’ Canada center (Taylor et al. 2017), but researchers have access to the raw data. “Only data that [is] collected outside of the detection session is deleted” (Taylor et al. 2017). Researchers can also organize the data on the MOTUS interface. Several factors influence radio strength, and consequently the ability of MOTUS and similar arrays to detect animals. For example, radio strength is highest when an antenna is oriented towards the receiver (Kays et al., 2011). Another factor that can affect wave propagation of the radio signal is vegetation cover; high vegetation will decrease signal strength. The number of antennas, as well as the spacing between these antennas, will affect detectability (Taylor et al., 2017). Birds flying overhead are also more likely to be detected than birds foraging on the ground (Taylor et al., 2017). These spots on the ground are known as dead zones, which are zones which should theoretically fall within the range of detection but are not actually reached by the MOTUS array’s signal due to different habitat variables. Scientists need to conduct more research to detect these “dead zones” and figure out a way to place them within the detectability of MOTUS technology. The overall goal of my honors research project at the McGill Bird Observatory is to better increase our understanding of the various factors that may interfere with the ability to detect radio tagged individuals at both a local and landscape scale. Specifically, this includes (1) determining how distance from the tower affects signal strength (long range telemetry), and (2) examining how habitat variables, such as canopy cover, shrub density, basal area and type of forest (conifer versus hardwood trees) affect signal strength in respect to previously established ‘dead zones’ in the zone of detection.
