The beating of a bird’s wings may soon be all the power Western Biology professor Chris Guglielmo needs to generate limitless data on his feathered friends.
Battery life has always been a limiting factor for wildlife tracking devices when studying the physiology of endurance flight and stopover refuelling of migratory birds. But with advancements in microelectronic components and vibrational energy harvesting, the possibility of these remote sensor units being powered solely from the motion of the birds themselves is taking flight.
“The vast majority of work, especially for small birds, is just with a battery. The limitation with this is battery life and weight, depending on the size of the bird,” said Guglielmo, noting the rule of thumb is the tag attached to the bird should weigh no more than 3 per cent of its body weight. “The electronics are very light, and the chip has become so small now. But it’s still the battery life that comes into play.”
The tags are programmable by the manufacturer on how often they send a radio pulse, or coded signal, to the researchers. But the more detection required for a specific research study, perhaps sending out every few seconds, the shorter the battery life.
“With a 12-second pulse rate, the battery will last around 30-40 days, which is pretty good for the migration work we do,” Guglielmo said. “With larger birds, say 30 to 50 grams, you could use a 1-gram tag on them, and it could have a battery that lasts six months to even a year. But even those batteries will die.”
Researchers have turned to small solar panels to help recharge the battery. However, for many forest-dwelling birds, the panels never received sufficient light to recharge the battery as required. Sometimes the bird will even preen their feather over top the solar panel, defeating the purpose.
Working with researchers at Cornell University, Guglielmo helped show the excess energy available from birds, and even bats, could be harvested without adversely affecting their overall effort.
“If we can we get around the solar panel idea, and use the vibrational energy of the bird, or bat, to recharge the device, it’s a great idea,” Guglielmo said. “These animals are moving all the time. When we’re studying them in flight, there is a regular movement – the frequency of the wings beat at, let’s say, 12-16 times per second. So, the piezoelectric device has to be tuned to match this frequency in order to optimize the energy.”
With the help of Western’s Advanced Facility for Avian Research (AFAR), acceleration measurements were taken on two bird species to understand variations in flapping frequency during steady flight. Researchers then calculated birds were capable of powering the type of microelectronic circuits used in bio-logging devices.
While this study only determines the feasibility of harvesting wing-fuelled energy, proto-types are coming soon. With an array of telemetry towers already spread across the country to assist researchers in collecting data from migratory birds, these latest findings will keep the data flowing for longer periods of time.
“This has been one of the major limitations on telemetry studies – the short lifespan of the tags. Anything you can do to stretch out the lifespan is a good thing,” Guglielmo said. “If you could continuously recharge that battery, you could estimate survival rates of birds – you could essentially follow them from birth to death.”
For larger birds, satellite transmitters can collect years of data. That wealth of information has been denied to those who study smaller birds – at least for now. “If we can get to the point where they would last longer, for years, then we’d really be in business,” Guglielmo said.
While a device may be a few years from taking flight, Guglielmo calls the theory behind the potential device sound. He expects future testing to be done at AFAR.
“When they do have the next generation ready, they will be coming back up and putting them on birds and flying them in our wind tunnel to see how much energy you can get out of a small bird,” he said. “There has been so much development in the last 10 years in telemetry devices. We’re doing things we’ve never done before.”