ON THE MAP
New bird-tracking technologies are leading to startling discoveries and helping revise migration pathways
IIt’s been a mystery since the study of bird migrations began: while scientists understand a great deal about where birds breed, they know less about where they spend other times and, sometimes, nothing about their travel routes. Over the last decade, though, researchers have started unlocking many of these unknowns using an array of evolving tracking technologies. The result: a stream of revelations about migratory birds’ journeys, their capabilities and critical destinations and hazards en route — essential information for conservation work. “There are some surprising findings,” says Darroch Whitaker, an ecosystem scientist with Parks Canada, in Rocky Harbour, N.L. “A lot of these birds are making astonishing non-stop movements.” Take Connecticut and blackpoll warblers, combined as one of six examples of such discoveries depicted on this map. These small songbirds, which weigh about as much as a triple-a battery, spend summer in Canada’s boreal forest and winter in South America. But in 2014 and 2016, researchers found that instead of flying south over land in the fall, they undertake a non-stop transatlantic marathon — upward of 2,500 kilometres — from the East Coast of the United States to various Caribbean islands before reaching their final destination. These conclusions emerge from light-sensing geolocators attached to the birds, one of the few devices small enough to be carried by birds this size. There are similar lightweight tags that record a bird’s GPS coordinates at pre-set intervals. Birds must be recaptured to collect this data. Other sensors, however, supply data that can be downloaded remotely, sometimes in real time. For example, slightly larger GPS tags can send location information when they’re in range of a receiver. Others link directly to satellites. Scientists using a third option, the Canadian-created Motus tracking system, fit birds with tiny nanotag transmitters that emit a radio signal detected by more than 350 ground-based tracking stations throughout North and South America whenever a tagged bird passes nearby. As the accompanying examples show, all of these methods — coupled with breakthroughs in DNA and isotope analysis that further pinpoint individual bird origins — are yielding remarkable results. “Migratory birds have always faced dangerous and daunting journeys, but human impacts have made such marathon flights all the more amazing,” says Bridget Stutchbury, a biology professor and Canada research chair in ecology and conservation biology at Toronto’s York University. “New technologies are important for advancing basic migration science, but also give us hope that population declines may someday be reversed.”
Whimbrel Whimbrels were among the first birds to show the power of migratory tracking technology. In 2008 and again in 2012, whimbrels fitted with satellite transmitter tags were tracked continuously between summer breeding grounds in Alaska and the Northwest Territories and wintering sites in Brazil. Often, the birds spent days aloft. Wilson’s warbler There are five known breeding regions for this species in Canada, and birds born in each carry distinctive genetic markers. In 2014, scientists used DNA to match birds in various wintering areas in Mexico to their areas of origin. In 2015 and 2016, dozens of these boreal breeders were tagged with tiny radio transmitters at overwintering grounds in Colombia. Researchers then logged segments of their springtime moves north with the Motus tracking system, revealing links between migration speeds — the fastest bird went 3,200 kilometres in a little more than three days, while some took weeks — and fuel availability at stopover sites.