Hi there,
there are no simple answers to these questions. As René points out, range is affected by many variables. Radio-signals work basically with line-of-sight. The higher your antenna, the more range you will likely get, but that may be at the expense of birds located very close to your station unless you have antennas configured to capture that area. In optimal conditions, there has been instances of detections happening 15-25 km away, but I expect those are relatively (very?) rare. Topography, vegetation, and even weather conditions will all have an impact. I would expect that a non-trivial number of detections go unnoticed, or cannot reliably be used. Someone here did some experiments with racing pigeons double-tagged (Lotek and GPS pinpoints), but this hasn’t been published yet that I am aware. Many fly-bys within a few km were not picked up by stations, if I recall correctly, but I may be mischaracterizing it. Many other instances have produce nice reliable detections. Fly-bys would have lower chance of detection than foraging or roosting birds that remain for longer in an area. You can try to ground truth your stations and see, but replicating the exact conditions of a tag on a bird that is in perpetual movement in different habitats and positions can be very challenging, to the point where your ground-truthing may not mean very much.
I haven’t seen the results from Terra in term of detection range. Without a standard antenna, I would expect it to be significant less than say a Yagi-based station or even an omni. These units are mainly aimed at the “mass“ market where the number of units compensate for the smaller detection range, which can nonetheless help complement the existing array. We’re certainly keen to learn more about whether Terra provides a viable solution under certain conditions.
The bulk of the costs of building a station probably remains the infrastructure (antenna, tower, wires). The cheaper reliable option that we can recommend probably remains a SensorGnome as currently suggested. The one area where you may be able to save a bit of money is a cheaper radio dongle, but those have not been really well tested, and we would not recommend them unless you are prepared to do your own evaluations, and if you don’t mind risking degraded data quality (missed detections). I think people who have tried have had mixed experiences.
A key challenge in signal processing is teasing out the noise, which may vary immensely depending on your location and the antenna orientation, from the true signal. There are probably useful progress that can be made to apply filtering on the antennas to help reduce noise and enhance true signals, but there is a significant risk that filtering may also remove more of the valid detections, so this is an area where we feel we need to proceed cautiously, and that would require people willing to do sufficient testing under a variety of conditions before we can recommend them. As an NGO, we have no benefit in promoting solutions that are more expensive than they need to be. If we ever find any cheaper and reliable solutions, we will definitely use them for our own arrays to the extent that we can support them, but just finding out takes time and costs money, as pointed out by René. Our efforts are thus aimed at the main products that we know work well.
I hope this helps!
Cheers
Denis
Denis Lepage dle...@bsc-eoc.org
Senior Director, Data Science and Technology
Birds Canada
PO Box 160, Port Rowan, ON N0E 1M0
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The Motus Wildlife Tracking System (Motus) is an international collaborative research network that uses coordinated automated radio telemetry to facilitate research and education on the ecology and conservation of migratory animals. Motus is a program of Birds
Canada in partnership with collaborating researchers and organizations. Learn more at
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The Motus Wildlife Tracking System (Motus) is an international collaborative research network that uses coordinated automated radio telemetry to facilitate research and education on the ecology and conservation of migratory animals. Motus is a program of Birds Canada in partnership with collaborating researchers and organizations. Learn more at https://motus.org
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