For over 50 years, traditional Radio-telemetry has been the cornerstone of tracking migratory studies. This is very useful to track movements of small animals with high temporal and spatial precision. But it also has its limitations because some of these former radio-telemetries may be quite impossible to use on tiny insects, animals or birds, because of their weight and size. Hence automated receivers, along with recent miniaturization and digital coding of tags, have improved the utility of radio-telemetry by allowing many individuals to be tracked continuously and simultaneously across broad landscapes. Tiny, digitally encoded tags (also called nanotags), are safely attached to an animal, insect, or bird, and these nanotags send out a unique identifying signal approximately every 30 seconds. If tagged animals fly by a strategically placed Motus tower with antenna tuned to the same frequency as the nanotags within a 6-mile distance approximately, the tag is automatically detected. Detection range depends on many factors such as tower height, antenna type and orientation, terrain, vegetation, and height of the animal relative to the tower.
Motus Receiving Stations and Towers:
Receiving Stations are equipped with a high-accuracy GPS sensor that allows for precise time synchronization and geolocation of the receiver. Automated radio towers can be arranged to track tagged animals or insects and are custom built in a variety of styles depending on their use. But essentially it consists of:
1) an automated radio receiver,
2) one to six antennas of various types can be used
3) the tower (or support structure which is also called the mast) structure and,
4) a power source either through an existing power source or through solar power for remote locations.
Antenna Receivers can accommodate multiple antennas tuned to a specific frequency and may be mounted to existing structures such as tall buildings, cell phone towers, or self-standing towers. The various components of the Antenna include the ‘elements’ which are little horizontal bars. The ‘boom’ is the center bar which basically holds the elements at a specified distance. Different antennas are designed to pick up different radio frequencies. There’s no electricity on the antenna, but rather the size of the antenna, the length of the elements, and the spacing between the elements on the boom create a parabola much like a tuning fork that is tuned into a specific frequency. These antennas do not send out any frequency or ping. Rather these are “passive” receiving devices for only the specific radio frequency.
Dense arrays of radio towers can be used to track local movements and if animals are detected by multiple towers, can be used to provide precise movement data. Coordinated arrays of automated radio towers, such as those organized by Bird Studies Canada’s Motus Wildlife Tracking System, allow for tracking of animals at continental scales. Animals passing within range of these towers are automatically detected and detection data is logged on to the receiver and passed on to the researchers that tagged that animal. Detection data can be downloaded directly from the receiver unit. Alternatively, towers can be connected to wired or wireless internet, or communicate through cell phone technology, which allows for around the clock remote access to detection data. As research and tracking technologies continue to improve, the international connectivity and migration ecology of birds and other tagged wildlife is better understood. The costs to install a receiver station vary and depends on the number and type of antennas. It also depends on whether existing infrastructure can be used to mount antennas, and the power source. Information about receiver deployments, including geographic coordinates, start and anticipated end date and time, and antenna configuration and orientation, is registered in the Motus database, and made available to all users.
Stay tuned for Series Article Part III: Nanotags and how they work